Windows: remove unused and leaked uniRootFileNameClone

In AFSCommonCreate remove the allocated but never used but leaked
'uniRootFileNameClone' Unicode string.

Change-Id: I02a4a1a2383c5a85f2a939b4d18e38def4cf2687
Reviewed-on: http://gerrit.openafs.org/9920
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>