Fix rollback of rolling upgrade in NameNode HA setup

This jira does the following:
1. When do rollback for rolling upgrade, we should call FSEditLog#initJournalsForWrite when initializing editLog (just like Upgrade in HA setup).
2. After the rollback, we also need to rename the md5 file and change its reference file name.
3. Add a new unit test to cover rollback with HA+QJM