addons: bridge: Fix KeyError when 'bridge-pvid' is not in the set 'bridge-vid'

Ticket: CM-11998
Reviewed By: roopa
Testing Done: used same config given in bug descreption

When we try to unconditionally remove 'pvid' from 'vids' set,
we run into KeyError if 'vids' set doesn't contain 'pvid'

Example configuration:
auto swp9
iface swp9
   mstpctl-portautoedge no

auto frontnet
iface frontnet
   bridge-vlan-aware yes
   bridge-ports swp9
   bridge-vids 10
   bridge-stp on

Signed-off-by: Nikhil <nikhil@cumulusnetworks.com>

addons/bridge.py

@@ -513,7 +513,7 @@ class bridge(moduleBase):
         vids1_ints = self._ranges_to_ints(vids1)
         vids2_ints = self._ranges_to_ints(vids2)
         set_diff = Set(vids1_ints).symmetric_difference(vids2_ints)
-        if pvid:
+        if pvid and int(pvid) in set_diff:
             set_diff = set_diff.remove(int(pvid))
         if set_diff:
             return False