[PATCH] NFSv4: Fix up races in nfs4_proc_setattr()

 If we do not hold a valid stateid that is open for writes, there is little
 point in doing an extra open of the file, as the RFC does not appear to
 mandate this...

 Make setattr use the correct stateid if we're holding mandatory byte
 range locks.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>