REGTEST: Wrong assumption in IP:port logging test.

In this reg test, as the client connection is not supposed to receive any
server response, we should try to "rxresp" but we should expect the client
connection to be closed by haproxy. This is done replacing "rxresp" by
"expect_close". Furthermore since dbb75ee3 vtest commit, calling "rxresp"
expects at least to receive a HTTP header as shown by Travis build
here: https://travis-ci.com/haproxy/haproxy/jobs/198126488.
diff --git a/reg-tests/log/wrong_ip_port_logging.vtc b/reg-tests/log/wrong_ip_port_logging.vtc
index 228c3fd..52857a2 100644
--- a/reg-tests/log/wrong_ip_port_logging.vtc
+++ b/reg-tests/log/wrong_ip_port_logging.vtc
@@ -57,7 +57,7 @@
 
 client c1 -connect ${h1_fe_1_sock} {
     txreq -url "/"
-    rxresp
+    expect_close
 } -run
 
 syslog Slg_1 -wait