threadshare/udpsink: Don't hold settings lock while calling into the sink pad handler to clear the clients
threadshare/udpsink: Don't hold settings lock while calling into the sink pad handler to clear the clients

Otherwise we can deadlock because of a lock order issue:
 - render() is called with the sink pad handler lock and takes the
   settings lock
 - clearing clients takes the sink pad handler lock

sdroege/rsplugin,sdroege/rsplugin