The billing history currently shows the Total amount from the Stripe
invoice. In fact, this value is just the amount deducted from the Stripe
balance. It does not reflect any deduction from promotional coupon or
bonus credits.
This patch adds the deducted amount form the promotional coupons and
bonus credits to the displayed amount in billing history. This way
customers have better understading of the total amount deducted from
their account balance on the satellite.
Change-Id: Ibd7f611a6cea0143a3059f39dd1d9ef21c264d8c
