getting new amount array in case of negativ payment fees

This change is necessary to disable payment discount on products with disabled discounts (like http://store.shopware.de/werbung-marketing/artikel-von-rabatt-ausschlieeen with the following events

$this->subscribeEvent('sBasket::sInsertSurchargePercent::before', 'beforeInsertDiscount');
$this->subscribeEvent('sBasket::sInsertSurchargePercent::after', 'afterInsertDiscount');
)