NFSv4: Ensure nfs_atomic_open set the dentry verifier on ENOENT

If the OPEN rpc call to the server fails with an ENOENT call, nfs_atomic_open
will create a negative dentry for that file, however it currently fails
to call nfs_set_verifier(), thus causing the dentry to be immediately
revalidated on the next call to nfs_lookup_revalidate() instead of following
the usual lookup caching rules.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 06e8cfc..6e62155 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1527,6 +1527,7 @@
 		case -ENOENT:
 			d_drop(dentry);
 			d_add(dentry, NULL);
+			nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
 			break;
 		case -EISDIR:
 		case -ENOTDIR: