[SPARK-19812] YARN shuffle service fails to relocate recovery DB acro…

…ss NFS directories

## What changes were proposed in this pull request?

Change from using java Files.move to use Hadoop filesystem operations to move the directories.  The java Files.move does not work when moving directories across NFS mounts and in fact also says that if the directory has entries you should do a recursive move. We are already using Hadoop filesystem here so just use the local filesystem from there as it handles this properly.

Note that the DB here is actually a directory of files and not just a single file, hence the change in the name of the local var.

## How was this patch tested?

Ran YarnShuffleServiceSuite unit tests.  Unfortunately couldn't easily add one here since involves NFS.
Ran manual tests to verify that the DB directories were properly moved across NFS mounted directories. Have been running this internally for weeks.

Author: Tom Graves <tgraves@apache.org>

Closes #17748 from tgravescs/SPARK-19812.