Discount not showing when discount_amount2 set and items added to cart individually

Discount node was conditionally added if there was an initial discount.
 If a product is configured to have a discount after quantity of one,
this discount node never gets created.  Detect if it exists, if not,
add it before changing the innerHTML.

Now, if a user adds individual items to their cart one at a time, after the first one is added, the discount amount shows for additional item discounts.  Before, a user would have to add 2 or more of the items to their cart off the bat to get the discount to appear.