Update setOrderSubtotalToPriceWithoutAdjustments to call calculateSubtotalWithoutAdjustments

The old code was pulling pricing directly off the order items which is incorrect because at this point in the pricing workflow we haven't set pricing information. This means that getTotal() on order item will return stale pricing.
Merge pull request #562 from jlutteringer/patch-1

Update setOrderSubtotalToPriceWithoutAdjustments to call calculateSubtot...