The #ships_with? method was being called ~800 times when loading the admin order edit page (with Aus production data), and triggering a new query each time it was called.
This ensures that Spree's shipping methods take into account the ones
the order's distributor uses.
This reimplements what `#available_to_order_with_distributor_check?`
used to do and it doesn't work with Spree 2.0.4.