NC migration development.

- Clear migration information from instance struct on destination after migration completed.
- Add handling of completed destination to migration_rollback_src().

Implements EUCA-5442, EUCA-5069, EUCA-5079.
NC migration development.

- Fix recently introduced deadlock in refresh_instance_info().

Implements EUCA-5442.
CC migration development.

- Added stub migration scheduler.
- Began replacing static destination-node selection with scheduler.
- Added migration rollback on destination in one possible case.
- Added saving of migration state in instance cache for reporting to CLC.

Implements EUCA-5069, EUCA-5079, EUCA-5071, EUCA-5175.
[CC] Corrected saving of migration state in instance cache.
[CC] Added saving of migration state in instance cache for reporting to CLC.

Implements EUCA-5071.
Merge remote-tracking branch 'origin/team/evac' into testing