Btrfs: run orphan cleanup on default fs root

This patch revert's commit

6c090a11e1c403b727a6a8eff0b97d5fb9e95cb5

Since it introduces this problem where we can run orphan cleanup on a
volume that can have orphan entries re-added.  Instead of my original
fix, Yan Zheng pointed out that we can just revert my original fix and
then run the orphan cleanup in open_ctree after we look up the fs_root.
I have tested this with all the tests that gave me problems and this
patch fixes both problems.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 009e3bd..87b2554 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1993,6 +1993,12 @@
 	if (!fs_info->fs_root)
 		goto fail_trans_kthread;
 
+	if (!(sb->s_flags & MS_RDONLY)) {
+		down_read(&fs_info->cleanup_work_sem);
+		btrfs_orphan_cleanup(fs_info->fs_root);
+		up_read(&fs_info->cleanup_work_sem);
+	}
+
 	return tree_root;
 
 fail_trans_kthread: