NFSv4.1: Ensure that layoutreturn uses the correct credential

We need to use the same credential as was used for the layoutget
and/or layoutcommit operations.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -6452,6 +6452,7 @@ int nfs4_proc_layoutreturn(struct nfs4_layoutreturn *lrp)
 		.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_LAYOUTRETURN],
 		.rpc_argp = &lrp->args,
 		.rpc_resp = &lrp->res,
+		.rpc_cred = lrp->cred,
 	};
 	struct rpc_task_setup task_setup_data = {
 		.rpc_client = lrp->clp->cl_rpcclient,

fs/nfs/pnfs.c

@@ -861,6 +861,7 @@ _pnfs_return_layout(struct inode *ino)
 	lrp->args.inode = ino;
 	lrp->args.layout = lo;
 	lrp->clp = NFS_SERVER(ino)->nfs_client;
+	lrp->cred = lo->plh_lc_cred;
 
 	status = nfs4_proc_layoutreturn(lrp);
 out: