addons: bridge: fix running_vids value when cache is stale

Ticket: CM-12552
Reviewed By: julien, nikhil
Testing Done: tested with failing config with bridge-access 1

This is similar to the fix done in the below commit for pvid:
"5061730ea5bf ("addons: bridge: fix default pvid handling in cases where
cache is stale")"

easier steps to reproduce:
- have a vlan aware bridge with more than one ports
- add 'bridge-access 1' to one of the ports
- boot the box with the config
- check that the  vlans are fine
- ifdown <interface_with_bridge_access_1>
- ifreload -a
- the interface with bridge_access 1 does
not have the pvid flag on vlan 1

This patch makes sure we assume the right running
vid and pvid value ie [1] and 1 if the
cache returns no values. vid = [1] and pvid = 1
are the kernel default/initial values for a port.

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>

addons/bridge.py

@@ -882,17 +882,21 @@ class bridge(moduleBase):
             (running_vids, running_pvid) = self._get_running_vids_n_pvid(
                                                         bportifaceobj.name)
 
-            if running_vids:
-                (vids_to_del, vids_to_add) = \
-                    self._diff_vids(vids_to_add, running_vids)
-
-            if not running_pvid:
+            if not running_vids and not running_pvid:
                 # There cannot be a no running pvid.
                 # It might just not be in our cache:
                 # this can happen if at the time we were
                 # creating the bridge vlan cache, the port
-                # was not part of the bridge
+                # was not part of the bridge. And we need
+                # to make sure both vids and pvid is not in
+                # the cache, to declare that our cache may
+                # be stale.
                 running_pvid = 1
+                running_vids = [1]
+
+            if running_vids:
+                (vids_to_del, vids_to_add) = \
+                    self._diff_vids(vids_to_add, running_vids)
 
             if running_pvid:
                 if running_pvid != pvid_int and running_pvid != 0: