As part of the implementation of multiple port bindings [1], add binding
activation support to the OVS agent. This will enable the execution in
OVS agents of the complete sequence of steps outlined in [1] during an
instance migration:
1) Create inactive port bindings for destination host
2) Migrate the instance to the destination host and plug its VIFs
3) Activate the port bindings in the destination host
4) Delete the port bindings for the source host
[1] https://review.openstack.org/#/c/309416/
Change-Id: Iabca39364ec95633b2a8891fc295b3ada5f4f5e0
Partial-Bug: #1580880
5c3bf12496