Fix VM-Vrouter ref update race.

When there is an add followed by delete, back-to-back, it is possible
VNC layer may not have updated the VM with vrouter info, as that ref
update is a seperate event.

Since VM's are always expected to vrouter info, if the ref is missing,
update that vrouter record in config db by reading from vnc.

Change-Id: I1771bad79ea6f58a768d9481224456fe7089534e
Closes-Bug: #1689905

src/container/kube-manager/kube_manager/vnc/vnc_pod.py

@@ -396,6 +396,12 @@ def vnc_pod_delete(self, pod_id):
         if not vm:
             return
 
+        # If this VM's vrouter info is not available in our config db,
+        # then it is a case of race between delete and ref updates.
+        # So explicitly update this entry in config db.
+        if not vm.virtual_router:
+            vm.update()
+
         self._clear_label_to_pod_cache(vm)
 
         if vm.virtual_router: