UDP: Fix session registration in lookup table

This fixes a bug where packets could be sent but not received when opening an UDP connection.

Change-Id: I0993dd806b277374232d551167970ab13a62dbf9
Signed-off-by: Aloys Augustin <aloaugus@cisco.com>
diff --git a/src/vnet/session/session.c b/src/vnet/session/session.c
index cd8da50..e51b138 100644
--- a/src/vnet/session/session.c
+++ b/src/vnet/session/session.c
@@ -880,6 +880,7 @@
   transport_connection_t *tc;
   transport_endpoint_cfg_t *tep;
   app_worker_t *app_wrk;
+  session_handle_t sh;
   session_t *s;
   int rv;
 
@@ -904,6 +905,9 @@
       return -1;
     }
 
+  sh = session_handle (s);
+  session_lookup_add_connection (tc, sh);
+
   return app_worker_connect_notify (app_wrk, s, opaque);
 }