CLOUDSTACK-2680: Async job expunge thread - expunge only:

1) Unfinished jobs that are yet to be processed.
2) Completed jobs

The jobs that are in process, will be skipped by the expunge thread

Conflicts:
	server/src/com/cloud/async/dao/AsyncJobDao.java
	server/src/com/cloud/async/dao/AsyncJobDaoImpl.java
	server/src/com/cloud/storage/snapshot/SnapshotManagerImpl.java
CLOUDSTACK-1974: Dedicate Guest VLAN Range - UI - Infrastructure menu - physical network - Guest - devailView - (1) add new tab "Dedicated VLAN Ranges" that list dedicated Guest VLAN Ranges under the physical network. (2) implement "Dedicate Guest VLAN Range" action.