Windows: use system CreateUuid instead of afs variant

Windows: use system CreateUuid instead of afs variant

The afs_create_uuid function on Windows results in
duplicate uuids being produced.  Windows provides its own
CreateUuid function.  Use it when afs_create_uuid is called.

Change-Id: Id7f14b13c003fb845d90b09c3ca40cf258a53dbc
Reviewed-on: http://gerrit.openafs.org/1937
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>