Remove promo adjustments from complete orders only

This was merged in both master and 1-3-stable a while ago. I noticed it's not in master anymore and I guess it may bring issues since in current master every time a promo is removed all of its adjustments are removed along, users might one to keep the adjustments from complete orders. Any special reason for not having this code in master @radar?

I think it was lost when the promo gem was merged into core.  I guess that merge generated tons of conflicts.