Btrfs: fix list delete warning when removing ordered root from the list

Commit b0244199 "Btrfs: don't wait for
the completion of all the ordered extents" introduced a bug that broke
the ordered root list:
 WARNING: CPU: 1 PID: 7119 at lib/list_debug.c:59 __list_del_entry+0x5a/0x98()

It is because we forgot to return the roots in the splice list to the
ordered list of the fs. Fix it.
Signed-off-by: NMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>
Signed-off-by: NChris Mason <chris.mason@fusionio.com>

fs/btrfs/ordered-data.c

@@ -638,6 +638,7 @@ void btrfs_wait_ordered_roots(struct btrfs_fs_info *fs_info, int nr)
 			WARN_ON(nr < 0);
 		}
 	}
+	list_splice_tail(&splice, &fs_info->ordered_roots);
 	spin_unlock(&fs_info->ordered_root_lock);
 }