btrfs: fix second lock in btrfs_delete_delayed_items()

Fix a real bug caught by coccinelle.

fs/btrfs/delayed-inode.c:1013:1-11: second lock on line 1013
Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>

fs/btrfs/delayed-inode.c

@@ -1028,9 +1028,10 @@ static int btrfs_delete_delayed_items(struct btrfs_trans_handle *trans,
 		btrfs_release_delayed_item(prev);
 		ret = 0;
 		btrfs_release_path(path);
-		if (curr)
+		if (curr) {
+			mutex_unlock(&node->mutex);
 			goto do_again;
-		else
+		} else
 			goto delete_fail;
 	}