ComputeNode Capacity support
ComputeNode Capacity support

The table represents the current state of compute nodes and will be
used by the scheduler when selecting a host.

Re: https://blueprints.launchpad.net/nova/+spec/scaling-zones

This is just the db & notification portion of the branch. The scheduler
portion is being deferring until comstuds branch gets merged since it
conflicts heavily.

NOTE: Compute notifications are now two-part.
There is a compute.instance.XXX.start event and a compute.instance.XXX.end
message instead of the previous compute.instance.XXX event (which is
the same as the .end message)

Change-Id: Ia8e68680cb0924c59df84f2eec858febf4926d65

openstack/oslo.versionedobjects,citrix-openstack-build/oslo.versionedobjects