CORD-3005 update app_label for VTN

Change-Id: Ib967dede94ed2e0657126a309ed3a50af5c700ac
(cherry picked from commit 72c7341e8801450d9555adeedf2f6582447f1adf)
diff --git a/xos/synchronizer/models/vtn.xproto b/xos/synchronizer/models/vtn.xproto
index 6be82da..759089d 100644
--- a/xos/synchronizer/models/vtn.xproto
+++ b/xos/synchronizer/models/vtn.xproto
@@ -1,5 +1,6 @@
 option kind = "VTN";
 option name = "vtn";
+option app_label = "vtn";
 
 message VTNService (Service){
      option verbose_name = "VTN Service";