nfsd: simplify process_lock

Similarly, this STALE_CLIENTID check is already handled by:

nfs4_preprocess_confirmed_seqid_op()->
        nfs4_preprocess_seqid_op()->
                nfsd4_lookup_stateid()->
                        set_client()->
                                STALE_CLIENTID()

(This may cause it to return a different error in some cases where
there are multiple things wrong; pynfs test SEQ10 regressed on this
commit because of that, but I think that's the test's fault, and I've
fixed it separately.)
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4state.c

@@ -6697,10 +6697,6 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 				&cstate->session->se_client->cl_clientid,
 				sizeof(clientid_t));
 
-		status = nfserr_stale_clientid;
-		if (STALE_CLIENTID(&lock->lk_new_clientid, nn))
-			goto out;
-
 		/* validate and update open stateid and open seqid */
 		status = nfs4_preprocess_confirmed_seqid_op(cstate,
 				        lock->lk_new_open_seqid,