HDFS-6545, we have noticed a couple of issues.
- The storage dir's VERSION file is not properly updated. This becomes a problem when there is a layout version change. We can have the finalization do storage.writeAll()
- OP_ROLLING_UPGRADE_FINALIZE cannot be replayed, once the corresponding OP_ROLLING_UPGRADE_START is consumed and a new fsimage is created (e.g. rollback image). On restart, NN terminates complaining it can't finalize something that it didn't start. We can make NN ignore OP_ROLLING_UPGRADE_FINALIZE if no rolling upgrade is in progress.