Remove ovs dependency in embrane plugin

This patch changes the dependency of the embrane plugin from ovs to ml2.
Existing users of the old entry point will be upgraded on a case-by-case
base as needed, therefore no generic upgrade procedure is required.

Change-Id: Id192fc32bd6ba7a8926eff1190070b8df5327129
Closes-Bug: #1343024
Merge "Remove ovs dependency in embrane plugin"