Awesome. The referred Articles helped me solve my ambari-metrics restart issue.
Here is the short form of the steps
1) Stop Ambari Metrics Collector and Grafana
2) Backup the embedded hbase and hbase-temp folders and deleted them. (The paths could differ from default. So I looked up the hbase.rootdir and hbase.tmp.dirproperties in Ambari > Ambari Metrics > Config for the appropriate path)
3) Restart Ambari Metrics Collector and Grafana
The Ambari Metrics Collector Started correctly without any errors.
Note: As you may have suspected, by deleting the existing hbase folder, you will loose the metrics history.