add NOTIFY for branch_route

kamailio/default.cfg

@@ -663,7 +663,7 @@ branch_route[MANAGE_BRANCH] {
 
 route[RELAY]
 {
-    if (is_method("INVITE|BYE|SUBSCRIBE|UPDATE")) {
+    if (is_method("INVITE|BYE|SUBSCRIBE|UPDATE|NOTIFY")) {
         if(!t_is_set("branch_route")) t_on_branch("MANAGE_BRANCH");
     }