btrfs: qgroup: use goto style to handle errors in add_delayed_ref()

Clean up resources using goto to get rid of repeated code.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Junchao Sun <sunjunchao2870@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>