HBASE-8397 improve unit-test coverage of package org.apache.hadoop.hbase.master.metrics (0.94)



git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1537607 13f79535-47bb-0310-9956-ffa450edef68
HBASE-8543 fix coverage org.apache.hadoop.hbase.rest.client

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.94@1537626 13f79535-47bb-0310-9956-ffa450edef68