registrar(k): reset dst uri in lookup

- upon lookup, dst uri is reset if no new dst uri is set from received
  or path, otherwise the coordinates of selected contact are not
  effective
- reported by Andreas Granig
(cherry picked from commit 53bb79cef5eb70e98472903ef84b5585cc798e65)

modules_k/registrar/lookup.c

@@ -105,6 +105,9 @@ int lookup(struct sip_msg* _m, char* _t, char* _s)
 			goto done;
 		}
 
+		/* reset next hop address */
+		reset_dst_uri(_m);
+
 		/* If a Path is present, use first path-uri in favour of
 		 * received-uri because in that case the last hop towards the uac
 		 * has to handle NAT. - agranig */