Add a bit of doc on the cleaning zk migration step

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1487935 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8631 Meta Region First Recovery

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1487939 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8657 Miscellaneous log fixups for hbase-it; tidier logging, fix a few NPEs

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1487945 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8638 add logging to compaction policy

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1487948 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8653 master seems to be deleting region tmp directory from under compaction

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1487961 13f79535-47bb-0310-9956-ffa450edef68