fix sip trace ack

credits to miconda & sergey-safarov

kamailio/default.cfg

@@ -885,6 +885,12 @@ onsend_route {
         xlog("L_INFO", "$ci|log|associate traffic from $var(user_source) with media server sip:$sndto(ip):$sndto(port)\n");
         $sht(associations=>$var(user_source))= "sip:" + $sndto(ip) + ":" + $sndto(port);
     }
+    
+    #!ifdef SIP_TRACE_ROLE
+    if (is_method("ACK")) {
+        sip_trace();
+    }
+    #!endif
 
     xlog("L_INFO", "$ci|pass|$sndfrom(ip):$sndfrom(port) -> $sndto(ip):$sndto(port)\n");
 }