[FIX] sale_coupon: dont show strikethrough if pricelist show discount

Using a pricelist set as `without_discount` will show a strikethrough price on
reward line (discount and free product).
This is happening because the program reward line (discount_line_product_id) is
created with the default 1$ price as this price is not usefull when computing
coupons. Only the line price is checked.

Now, we create a reward line with a -1 000 000$ price to prevent this UI
behavior.

Step to reproduce:
  - Activate pricelist (Sales>Config>Settings>Pricelist formulas)
  - Activate discounts in Sales Configuration (Manual discount on order lines)
  - Set pricelist to 'Show public price & discount to the customer'
  - Add a discount in your cart
  - There in a strikethrough price of $1 above the discount line price

task-1878245

0 files changed, 0 insertions, 0 deletions