NC maintenance-mode development.

- Source node should not accept migration commit if not ready.
- Destination node should not complain if migrationTime is 0.
- Source node libvirt migration failure should trigger rollback.

Implements EUCA-5442, EUCA-5079, EUCA-5443, EUCA-5069.
CC maintenance-mode development: state handling/logging.

Implements EUCA-5079, EUCA-5069.
Merge branch 'dev/juphoff/evac' of git.eucalyptus-systems.com:eucalyptus into dev/juphoff/evac
NC maintenance-mode development.

- Correct error codes and log messages.

Implements EUCA-5079.
CC maintenance-mode development.

- migration_handler() should not process destination nodes that are
  in Teardown(ready) state.

Implements EUCA-5069, EUCA-5079.
Merge remote-tracking branch 'origin/team/evac' into testing