Restore ovs-vswitchd VLAN, mirror, bonding, QoS features ("xflow" only).

Restore ovs-vswitchd VLAN, mirror, bonding, QoS features ("xflow" only).

The OVS restructuring from "master" to "wdp" unfortunately left behind a
of features that were implemented by ovs-vswitchd (rather than ofproto).
This commit starts to add them back in.  They are still not implemented
the "right way", because unfortunately that will require more time, but
they will work specifically with the wdp-xflow backend.

The netflow and sflow features need more work.