HBASE-12322 Add Clean command to ITBLL

Signed-off-by: stack <stack@apache.org>

Conflicts:
	hbase-it/src/test/java/org/apache/hadoop/hbase/test/IntegrationTestBigLinkedList.java
Add missing license
HBASE-12328 Need to separate JvmMetrics for Master and RegionServer (Sanghyun Yun)