On shutdown, first stop listeners, then modules (thanks to Vishal Xica)(EJAB-1566)

src/ejabberd_app.erl

@@ -78,6 +78,7 @@ start(_, _) ->
 %% This function is called when an application is about to be stopped,
 %% before shutting down the processes of the application.
 prep_stop(State) ->
+    ejabberd_listener:stop_listeners(),
     stop_modules(),
     ejabberd_admin:stop(),
     broadcast_c2s_shutdown(),