REGTEST: Make this reg test be Linux specific.

This patch reverts 9ffb88 commit (REGTEST: Be less Linux specific with a syslog
regex.) and makes this script be Linux specific.
diff --git a/reg-tests/checks/4be_1srv_smtpchk_httpchk_layer47errors.vtc b/reg-tests/checks/4be_1srv_smtpchk_httpchk_layer47errors.vtc
index ffd3123..e3c959f 100644
--- a/reg-tests/checks/4be_1srv_smtpchk_httpchk_layer47errors.vtc
+++ b/reg-tests/checks/4be_1srv_smtpchk_httpchk_layer47errors.vtc
@@ -1,6 +1,7 @@
 varnishtest "Check: smptchk option"
 feature ignore_unknown_macro
 
+#EXCLUDE_TARGETS=freebsd,osx,generic
 #REGTEST_TYPE=slow
 
 barrier b cond 3
@@ -29,7 +30,7 @@
     recv
     expect ~ "[^:\\[ ]\\[${h1_pid}\\]: Proxy be3 started"
     recv
-    expect ~ "[^:\\[ ]\\[${h1_pid}\\]: Health check for server be3/srv3 failed, reason: Layer4 .* check duration: [[:digit:]]+ms, status: 0/1 DOWN."
+    expect ~ "[^:\\[ ]\\[${h1_pid}\\]: Health check for server be3/srv3 failed, reason: Layer4 connection problem, info: \"General socket error \\(Network is unreachable\\)\", check duration: [[:digit:]]+ms, status: 0/1 DOWN."
 } -start
 
 syslog S4 -level notice {