REGTEST: Fix LEVEL 4 script 0 of "connection" module.

Prevent this script from creating a UNIX socket in ${testdir} which
is the parent directory of the script. Prefer use ${tmpdir} which
is the temporary working directory for the script.

reg-tests/connection/b00000.vtc

@@ -36,14 +36,14 @@ haproxy h1 -conf {
 
     listen http
         bind-process 1
-        bind unix@${testdir}/http.socket accept-proxy name ssl-offload-http
+        bind unix@${tmpdir}/http.socket accept-proxy name ssl-offload-http
         option forwardfor
 
     listen ssl-offload-http
         option httplog
         bind-process 2-4
         bind "fd@${ssl}" ssl crt ${testdir}/common.pem ssl no-sslv3 alpn h2,http/1.1
-        server http unix@${testdir}/http.socket send-proxy
+        server http unix@${tmpdir}/http.socket send-proxy
 } -start