DNS name resolution order for haproxy config in test env

Indicate in what order the server's address should be resolved upon
startup if it uses an FQDN.

fe-test-common/overlay/opt/frontend/config/common/haproxy_base.j2

@@ -42,6 +42,9 @@ defaults
     timeout server 17s
     timeout http-request 5s
     balance roundrobin
+
+    # never fail on address resolution
+    default-server init-addr libc,none
 {% endblock defaults %}
 
 {% block stats %}