Use "updateShippingPackage" for better synchronisation with shipping package

[wernerkrauss]

Related to silvershop/silvershop-shipping#62

The discounts module should use "updateShippingPackage", so the shipping costs can be calculated from SubTotal - Discounts.

In some cases SubTotal can mean "free shipping", but "SubTotal - Discount" is less money, so shipping costs will apply.

[RVXD]

We tried to fix it this way, but it creates an infinite loop in the calculation process. We fixed it by supplying the running total to the shipping calculator.