bridge: T1673: add missing VLAN bridge member migration
bridge: T1673: add missing VLAN bridge member migration

VLAN interfaces assigned to a bridge as member have not been migrated so far.
This was the case for vif, vif-s and vif-c interfaces. The migration code has
been generalized in migrate_bridge() so it is re-usable for regular interfaces,
vif, vif-s and vif-c interfaces - all now use the same code.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x