Fixes a Hyper-V live migration issue

Fixes Bug: 1129091

Adds return values to check_can_live_migrate_destination
and check_can_live_migrate_source and some debug log notifications.

Removes the deprecated compare_cpu method.

The base class documentation currently does not specify any return
value constraint for the aforementioned methods so the return type
has been inferred from nova/compute/manager.py.

Change-Id: Ic4b09be4f3958f6d22a9ee41bc8037d2c2e95c0b
Merge "Fixes a Hyper-V live migration issue"