Altering get_bridge_name_vswitch() so that it works correctly with
ports connected to a "fake bridge" device (e.g., vlan-tagged
networks).  Most ovs-* commands will not work with a fake bridge
device, so this function needs to return the true parent bridge
device name, not the fake bridge.  Otherwise, subsequent calls
in this script to configure port locking via ovs-ofctl will
(silently) fail, and port locking will not activate.