[master] Display start time of Master and RegionServer

Author: rsadziak

Summary: Added start time of Master and RegionServer

Test Plan: Start time can be viewed on info page of servers

Reviewers: gauravm

Reviewed By: gauravm

CC: bhall, hbase-eng@

Differential Revision: https://phabricator.fb.com/D1035550

Task ID: 2977295

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1538015 13f79535-47bb-0310-9956-ffa450edef68