Move the extent_op cleanup for an empty head ref to a helper function to
help simplify __btrfs_run_delayed_refs.
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>