NFSv4: Ensure the LOCK call cannot use the delegation stateid

Defensive patch to ensure that we copy the state->open_stateid, which
can never be set to the delegation stateid.

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

fs/nfs/nfs4proc.c

@@ -4793,7 +4793,7 @@ static void nfs4_lock_prepare(struct rpc_task *task, void *calldata)
 		if (nfs_wait_on_sequence(data->arg.open_seqid, task) != 0) {
 			goto out_release_lock_seqid;
 		}
-		data->arg.open_stateid = &state->stateid;
+		data->arg.open_stateid = &state->open_stateid;
 		data->arg.new_lock_owner = 1;
 		data->res.open_seqid = data->arg.open_seqid;
 	} else