session/vcl: improve fifo tx notifications

Change-Id: Ied476c417c8ba5b4d7c615125c36eecd9ca64fbc
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/session/session.c b/src/vnet/session/session.c
index 4cf0f9e..c56712b 100644
--- a/src/vnet/session/session.c
+++ b/src/vnet/session/session.c
@@ -557,7 +557,11 @@
   if (PREDICT_FALSE (!app))
     return -1;
 
-  return app_worker_lock_and_send_event (app, s, FIFO_EVENT_APP_TX);
+  if (app_worker_lock_and_send_event (app, s, FIFO_EVENT_APP_TX))
+    return -1;
+
+  svm_fifo_clear_tx_ntf (s->server_tx_fifo);
+  return 0;
 }
 
 /**