Add OpenDaylight ML2 MechanismDriver

This commit adds support for OpenDaylight as an ML2 MechanismDriver. The
ODL MechanismDriver does not need an agent since ODL itself handles
programming bridges, tunnels, and ports on the host.

Implements bp ml2-opendaylight-mechanism-driver

Change-Id: Ic1612cd3e8efd39e74a7ed8cff28e91b1f388971
Merge "Add OpenDaylight ML2 MechanismDriver"