[NC] Block attempts to migrate instances when same node is designated as source and destination.

Implements EUCA-5175.
CC migration development

- Change all schedulers to only schedule ENABLED nodes.
- Send a separate destination 'prepare' request for each instance.

Implements EUCA-5069, EUCA-5175.
CC maintenance-mode development.

- [CC] code clean-ups.
- [CC] Extend migraton calls to handle specifying destination-host whitelist/blacklist.
- [CC] Implement migrations specified by instance ID.

Implements EUCA-5069, EUCA-5175.
[CC] Implement ROUNDROBIN scheduling for migrations.

Implements EUCA-5175.
Merge remote-tracking branch 'origin/dev/juphoff/evac' into team/evac
Merge remote-tracking branch 'origin/testing' into dev/juphoff/evac-testing

Conflicts:
	cluster/handlers.c
	cluster/server-marshal.c
	node/handlers.c
Merge remote-tracking branch 'origin/testing' into dev/juphoff/evac-test
[CC] Implement migration inclusion/exclusion host lists and specific-node migrations.

Implements EUCA-5175.
[CC] Improve handling of migration host exclusion list.

Implements EUCA-5175.
Merge branch 'dev/juphoff/evac' into dev/juphoff/evac-test

Conflicts:
	cluster/handlers.c
	util/misc.c
	util/misc.h
[CC] Implement handling of migration rollback on destination node.

Implements EUCA-5069, EUCA-5079.
Merge branch 'dev/juphoff/evac' into dev/juphoff/evac-test

Conflicts:
	cluster/handlers.c
Merge remote-tracking branch 'origin/testing' into dev/juphoff/evac-test
Merge remote-tracking branch 'origin/testing' into dev/juphoff/evac-test