REGTESTS: disable inter-thread idle connection sharing on sensitive tests

Some regtests involve multiple requests from multiple clients, which can
be dispatched as multiple requests to a server. It turns out that the
idle connection sharing works so well that very quickly few connections
are used, and regularly some of the remaining idle server connections
time out at the moment they were going to be reused, causing those random
"HTTP header incomplete" traces in the logs that make them fail often. In
the end this is only an artefact of the test environment.

And indeed, some tests like normalize-uri which perform a lot of reuse
fail very often, about 20-30% of the times in the CI, and 100% of the
time in local when running 1000 tests in a row. Others like ubase64,
sample_fetches or vary_* fail less often but still a lot in tests.

This patch addresses this by adding "tune.idle-pool.shared off" to all
tests which have at least twice as many requests as clients. It proves
very effective as no single error happens on normalize-uri anymore after
10000 tests. Also 100 full runs of all tests yield no error anymore.

One test is tricky, http_abortonclose, it used to fail ~10 times per
1000 runs and with this workaround still fails once every 1000 runs.
But the test is complex and there's a warning in it mentioning a
possible issue when run in parallel due to a port reuse.
diff --git a/reg-tests/cache/caching_rules.vtc b/reg-tests/cache/caching_rules.vtc
index c20a720..114b2fd 100644
--- a/reg-tests/cache/caching_rules.vtc
+++ b/reg-tests/cache/caching_rules.vtc
@@ -78,6 +78,12 @@
 } -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         ${no-htx} option http-use-htx
diff --git a/reg-tests/cache/expires.vtc b/reg-tests/cache/expires.vtc
index 51c7487..037f09f 100644
--- a/reg-tests/cache/expires.vtc
+++ b/reg-tests/cache/expires.vtc
@@ -40,6 +40,12 @@
 } -start
 
 haproxy h1 -conf {
+       global
+               # WT: limit false-positives causing "HTTP header incomplete" due to
+               # idle server connections being randomly used and randomly expiring
+               # under us.
+               tune.idle-pool.shared off
+
        defaults
                mode http
                ${no-htx} option http-use-htx
diff --git a/reg-tests/cache/if-modified-since.vtc b/reg-tests/cache/if-modified-since.vtc
index e491e46..8ae1cce 100644
--- a/reg-tests/cache/if-modified-since.vtc
+++ b/reg-tests/cache/if-modified-since.vtc
@@ -40,6 +40,12 @@
 } -start
 
 haproxy h1 -conf {
+       global
+               # WT: limit false-positives causing "HTTP header incomplete" due to
+               # idle server connections being randomly used and randomly expiring
+               # under us.
+               tune.idle-pool.shared off
+
        defaults
                mode http
                ${no-htx} option http-use-htx
diff --git a/reg-tests/cache/if-none-match.vtc b/reg-tests/cache/if-none-match.vtc
index c5391c9..ba3336a 100644
--- a/reg-tests/cache/if-none-match.vtc
+++ b/reg-tests/cache/if-none-match.vtc
@@ -25,6 +25,12 @@
 } -start
 
 haproxy h1 -conf {
+       global
+               # WT: limit false-positives causing "HTTP header incomplete" due to
+               # idle server connections being randomly used and randomly expiring
+               # under us.
+               tune.idle-pool.shared off
+
        defaults
                mode http
                ${no-htx} option http-use-htx
diff --git a/reg-tests/cache/sample_fetches.vtc b/reg-tests/cache/sample_fetches.vtc
index 73e6e1b..973b3ad 100644
--- a/reg-tests/cache/sample_fetches.vtc
+++ b/reg-tests/cache/sample_fetches.vtc
@@ -44,6 +44,12 @@
 } -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         ${no-htx} option http-use-htx
diff --git a/reg-tests/cache/vary.vtc b/reg-tests/cache/vary.vtc
index f3425d0..0b5d139 100644
--- a/reg-tests/cache/vary.vtc
+++ b/reg-tests/cache/vary.vtc
@@ -127,6 +127,12 @@
 } -start
 
 haproxy h1 -conf {
+       global
+               # WT: limit false-positives causing "HTTP header incomplete" due to
+               # idle server connections being randomly used and randomly expiring
+               # under us.
+               tune.idle-pool.shared off
+
        defaults
                mode http
                ${no-htx} option http-use-htx
diff --git a/reg-tests/cache/vary_accept_encoding.vtc b/reg-tests/cache/vary_accept_encoding.vtc
index 185ad05..852ac29 100644
--- a/reg-tests/cache/vary_accept_encoding.vtc
+++ b/reg-tests/cache/vary_accept_encoding.vtc
@@ -92,6 +92,12 @@
 
 
 haproxy h1 -conf {
+       global
+               # WT: limit false-positives causing "HTTP header incomplete" due to
+               # idle server connections being randomly used and randomly expiring
+               # under us.
+               tune.idle-pool.shared off
+
        defaults
                mode http
                ${no-htx} option http-use-htx
diff --git a/reg-tests/compression/etags_conversion.vtc b/reg-tests/compression/etags_conversion.vtc
index 0cae679..48e7955 100644
--- a/reg-tests/compression/etags_conversion.vtc
+++ b/reg-tests/compression/etags_conversion.vtc
@@ -106,6 +106,12 @@
 
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         ${no-htx} option http-use-htx
diff --git a/reg-tests/compression/vary.vtc b/reg-tests/compression/vary.vtc
index 0a060e4..a905f9c 100644
--- a/reg-tests/compression/vary.vtc
+++ b/reg-tests/compression/vary.vtc
@@ -61,6 +61,12 @@
 
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         ${no-htx} option http-use-htx
diff --git a/reg-tests/converter/json_query.vtc b/reg-tests/converter/json_query.vtc
index ade7b4c..b420942 100644
--- a/reg-tests/converter/json_query.vtc
+++ b/reg-tests/converter/json_query.vtc
@@ -9,6 +9,12 @@
 } -repeat 8 -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
 	mode http
 	timeout connect 1s
diff --git a/reg-tests/converter/secure_memcmp.vtc b/reg-tests/converter/secure_memcmp.vtc
index f9341f9..b16e021 100644
--- a/reg-tests/converter/secure_memcmp.vtc
+++ b/reg-tests/converter/secure_memcmp.vtc
@@ -16,6 +16,12 @@
 } -repeat 7 -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
 	mode http
 	timeout connect 1s
diff --git a/reg-tests/http-messaging/h1_to_h1.vtc b/reg-tests/http-messaging/h1_to_h1.vtc
index 5b02f17..c7d0085 100644
--- a/reg-tests/http-messaging/h1_to_h1.vtc
+++ b/reg-tests/http-messaging/h1_to_h1.vtc
@@ -115,6 +115,12 @@
 } -repeat 3 -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
 	mode http
 	${no-htx} option http-use-htx
diff --git a/reg-tests/http-messaging/h2_to_h1.vtc b/reg-tests/http-messaging/h2_to_h1.vtc
index 481aded..0d2b1e5 100644
--- a/reg-tests/http-messaging/h2_to_h1.vtc
+++ b/reg-tests/http-messaging/h2_to_h1.vtc
@@ -34,6 +34,12 @@
 } -repeat 2 -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
 	#log stdout format raw daemon
 	mode http
diff --git a/reg-tests/http-messaging/http_abortonclose.vtc b/reg-tests/http-messaging/http_abortonclose.vtc
index c074982..ae0d237 100644
--- a/reg-tests/http-messaging/http_abortonclose.vtc
+++ b/reg-tests/http-messaging/http_abortonclose.vtc
@@ -46,6 +46,12 @@
 } -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         ${no-htx} option http-use-htx
diff --git a/reg-tests/http-messaging/http_bodyless_response.vtc b/reg-tests/http-messaging/http_bodyless_response.vtc
index f45a7d6..6f36545 100644
--- a/reg-tests/http-messaging/http_bodyless_response.vtc
+++ b/reg-tests/http-messaging/http_bodyless_response.vtc
@@ -30,6 +30,12 @@
 } -repeat 2 -start
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         ${no-htx} option http-use-htx
diff --git a/reg-tests/http-rules/except-forwardfor-originalto.vtc b/reg-tests/http-rules/except-forwardfor-originalto.vtc
index 942c4e2..bb346dd 100644
--- a/reg-tests/http-rules/except-forwardfor-originalto.vtc
+++ b/reg-tests/http-rules/except-forwardfor-originalto.vtc
@@ -7,6 +7,12 @@
 feature ignore_unknown_macro
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         timeout connect 1s
diff --git a/reg-tests/http-rules/http_return.vtc b/reg-tests/http-rules/http_return.vtc
index a50f1fe..8189028 100644
--- a/reg-tests/http-rules/http_return.vtc
+++ b/reg-tests/http-rules/http_return.vtc
@@ -6,6 +6,12 @@
 feature ignore_unknown_macro
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         timeout connect 1s
diff --git a/reg-tests/http-rules/normalize_uri.vtc b/reg-tests/http-rules/normalize_uri.vtc
index 47032d9..42c4c42 100644
--- a/reg-tests/http-rules/normalize_uri.vtc
+++ b/reg-tests/http-rules/normalize_uri.vtc
@@ -12,6 +12,10 @@
 
 haproxy h1 -conf {
     global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
         expose-experimental-directives
 
     defaults
diff --git a/reg-tests/lua/set_var.vtc b/reg-tests/lua/set_var.vtc
index fc21b41..af4cbf1 100644
--- a/reg-tests/lua/set_var.vtc
+++ b/reg-tests/lua/set_var.vtc
@@ -6,6 +6,12 @@
 
 haproxy h1 -conf {
     global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
+    global
         lua-load ${testdir}/set_var.lua
 
     frontend fe1
diff --git a/reg-tests/lua/txn_get_priv-thread.vtc b/reg-tests/lua/txn_get_priv-thread.vtc
index 77e333d..6f5d632 100644
--- a/reg-tests/lua/txn_get_priv-thread.vtc
+++ b/reg-tests/lua/txn_get_priv-thread.vtc
@@ -7,6 +7,11 @@
 
 haproxy h1 -conf {
     global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
         lua-load-per-thread ${testdir}/txn_get_priv.lua
         lua-load-per-thread ${testdir}/txn_get_priv-print_r.lua
 
diff --git a/reg-tests/sample_fetches/ubase64.vtc b/reg-tests/sample_fetches/ubase64.vtc
index d6973e3..0122bad 100644
--- a/reg-tests/sample_fetches/ubase64.vtc
+++ b/reg-tests/sample_fetches/ubase64.vtc
@@ -5,6 +5,12 @@
 feature ignore_unknown_macro
 
 haproxy h1 -conf {
+    global
+        # WT: limit false-positives causing "HTTP header incomplete" due to
+        # idle server connections being randomly used and randomly expiring
+        # under us.
+        tune.idle-pool.shared off
+
     defaults
         mode http
         timeout connect 1s
diff --git a/reg-tests/webstats/webstats-scope-and-post-change.vtc b/reg-tests/webstats/webstats-scope-and-post-change.vtc
index a77483b..fe8b333 100644
--- a/reg-tests/webstats/webstats-scope-and-post-change.vtc
+++ b/reg-tests/webstats/webstats-scope-and-post-change.vtc
@@ -8,6 +8,11 @@
 
 haproxy h1 -conf {
   global
+    # WT: limit false-positives causing "HTTP header incomplete" due to
+    # idle server connections being randomly used and randomly expiring
+    # under us.
+    tune.idle-pool.shared off
+
     stats socket /tmp/haproxy.socket level admin
 
   defaults