DefaultMetricsSystemInitializer should be called during HMaster or HRegionServer creation

Concern is the jvm metrics somehow started populating with process name as IO instead of expected RegionServer/Master. See https://issues.apache.org/jira/browse/HBASE-27966 for RCA and a stop-gap fix. But this does not fix the problem, just hides it. We should be able to figure out why the metrics is getting initialized in BaseSourceImpl instead of during HMaster/RS process creation. We may need to refactor/move the code around to fix the same.

See review comments of https://github.com/apache/hbase/pull/5323 for more details.

CC: zhangduo