HBASE-8611. Improve test coverage in pkg org.apache.hadoop.hbase.mapred

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1537567 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/trunk@1537622 13f79535-47bb-0310-9956-ffa450edef68