HMaster.getCompactionState's return result about table compaction state is not quite right

1. The table compaction state should be NONE if all of those regions is online and is not compacting.

2. The Table compaction state should be null if one of those regions is not online and others is not compacting.  null means that the table compaction state we obtained is UNKOWN.

3. The Table compaction state should be minor/major when there are regions which is compacting