[HBASE-9972] Make HBase export metrics to JMX by default, instead of to NullContext

Author: gauravm

Summary:
I was debugging the metrics issue in the swift branch, and found that HBase doesn't export to JMX by default. The JMX server is being spun-up anyways in single node setup, we might as well export the metrics to it.

Copied the hadoop-metrics.properties file from titan shadow 25.

Test Plan: Tested it by spinning up the cluster, and verifying that the metrics show up on JConsole

Reviewers: adela, manukranthk, fan, aaiyer

Reviewed By: adela

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D1057243

Task ID: 3193706

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1542373 13f79535-47bb-0310-9956-ffa450edef68