[NC] Improve debug logging during migration verification.

Implements EUCA-5178.
[CC] Make migration-prepare calls to destination nodes asynchronous.

Implements EUCA-5069, EUCA-5175.
Merge branch 'dev/juphoff/evac-test' of git.eucalyptus-systems.com:eucalyptus into dev/juphoff/evac-test
fixes EUCA-5707: set proper instance migration state when migration fails
[NC] Remove assertion, improve migration logging.

Implements EUCA-5178.
CC migration development:

- Ensure migration-destination IP address is sent to source during commit call
- Remove implementation warning about rollbacks
- Improve error handling for incorrect commit requests

Implements EUCA-5069, EUCA-5079, EUCA-5175.
[CC] Use (wrapped) ROUNDROBIN scheduler for migrations regardless of configured scheduler.

Implements EUCA-5175.
[NC] logging improvements
Merge remote-tracking branch 'origin/testing' into dev/juphoff/evac-test
Merge branch 'testing' of https://github.com/mdshaonimran/eucalyptus into dev/juphoff/evac-test
Further cleanup of migration info in instance struct if migration rollback called with buggy host info.

Fixes EUCA-5707.
Rename migration_rollback_src() to migration_rollback().
Merge remote-tracking branch 'origin/testing' into dev/juphoff/evac-test