Support for Namenode HA for non-idempotent operations

In hadoop 2 HA, non-idempotent operations are not retried at the hdfs side. This is by design as retrying a non-idempotent operation might not be a good design choice for some use case.
HBase needs to handle the retries for such operations at its end.
With HBase-7806, there is already some work going on for file system abstractions. There, HReginFileSystem sits as an abstraction between region and FS. This jira is a move in the same direction, where it adds retry functionality for non-idempotent calls such as create, rename and delete in HRegionFileSystem class.