session: no reply on app del worker with sapi

With socket api, applications should not expect reply after worker del
msg. VCL in particular closes the socket after it enqueues the message.

Found by ASAN.

Type: fix

Signed-off-by: Dmitry Valter <d-valter@yandex-team.com>
Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I1be02a0cde6b96a96edb709f3fe30bbc01ff2d24

src/vnet/session/session_api.c

@@ -1463,6 +1463,10 @@ sapi_add_del_worker_handler (app_namespace_t * app_ns,
 
 done:
 
+  /* With app sock api socket expected to be closed, no reply */
+  if (!mp->is_add && appns_sapi_enabled ())
+    return;
+
   msg.type = APP_SAPI_MSG_TYPE_ADD_DEL_WORKER_REPLY;
   rmp = &msg.worker_add_del_reply;
   rmp->retval = rv;