always set contact alias on a reply

* so that acks go to proper address

(cherry picked from commit 248f758ec5)

kamailio/nat-traversal-role.cfg

@@ -101,6 +101,10 @@ route[NAT_MANAGE]
         setbflag(FLB_NATB);
    }
 
+   if (is_reply()) {
+       set_contact_alias();
+   }
+
    if (!(isflagset(FLT_NATS) || isbflagset(FLB_NATB))) {
         xlog("L_DEBUG", "$ci|log|NOT SETTING\n");
         return;