REGTEST: fix the race conditions in hmac.vtc

A "Connection: close" header is added to responses to avoid any connection
reuse. This should avoid any "HTTP header incomplete" errors.

(cherry picked from commit 7956aa14d34baf49741c5bd356ce06a6ab2711a4)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 1b767f6b82388e90c9cfe2098a87461a1206c73c)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 0c34554950d7f2a2964624c36bd806c2dca057f3)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 182a328ddef4f6522b50705d7a691fe647035cae)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/reg-tests/converter/hmac.vtc b/reg-tests/converter/hmac.vtc
index f9d9d35..391e04a 100644
--- a/reg-tests/converter/hmac.vtc
+++ b/reg-tests/converter/hmac.vtc
@@ -7,7 +7,7 @@
 
 server s1 {
 	rxreq
-	txresp
+	txresp -hdr "Connection: close"
 } -repeat 2 -start
 
 haproxy h1 -conf {