Windows: RDR_CleanupFile FSync only files

If the cm_scache type is something other than a file, there
is no point performing an FSync.   Do not incur the overhead.

Take into account any outstanding AsyncStore operations that
might be in-flight.

Change-Id: I66cd59cbcd81f2a7639e478832f921ac393ea3ae
Reviewed-on: http://gerrit.openafs.org/8972
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>