Windows: FilePhysicalNameInfo query AFS prefix

In response to the FilePhysicalNameInformation query the AFS redirector
failed to include the server name in the response.  Since the constructed
name is the same as the FileNameInformation query create a helper function
AFSGetFullFileName() to populate the file name into the provided buffer
and use it to satisfy both queries.

Change-Id: I78eef49a9902341c751d942a395921bb687c503b
Reviewed-on: http://gerrit.openafs.org/11488
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>