The PowerVM REST API allows a handler to be registered for events
from PowerVM. From the events it can be determined if a VM has
had a state change. This change set registers for those events
and determines if the state change is one that should trigger
an instance life cycle event to the compute manager. The compute
manager then can sync the power state between OpenStack and
PowerVM. Normally, _sync_power_states is only called via a
periodic task which defaults to 10 minute intervals.
Change-Id: I33363d4b9dfef3fafc9125dd283660417dbf3186