ifupdown2 patch to properly remove address-virtual mac addresses

Ticket: CM-6702
Reviewed By: roopa
Testing Done: unit and smoke tested with ifupdown2 suite

When address-virtual mac adddress is modified, removed from an SVI, or the SVI is removed,
the permanent mac address is not removed.

This patch addresses all three cases but creating a global statemanager instance
and removing address-virtual FDB entries that were previously configured.

ifupdown/statemanager.py

@@ -174,3 +174,5 @@ class stateManager():
         else:
             for ifacename, ifaceobjs in self.ifaceobjdict.items():
                 [i.dump(self.logger) for i in ifaceobjs]
+
+statemanager_api = stateManager()