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>
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 2f86115..89ca75f 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -861,6 +861,7 @@
 	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: