[PATCH] NFS: Fix error handling in nfs_direct_write_result()

If the RPC call tanked, we should not be checking the return value
of data->res.verf->committed, since it is unlikely to even be
initialised.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>