role adjustments not applied

Role adjustments were not applied when products were purchased. I found that the node passed to "ec_roles_process_purchase" had not been fully populated. In particular, "ec_roles_load" had not been called to add the "buy_add" and "buy_del" arrays.

I added a call to "ec_roles_load" within "ec_roles_process_purchase", which works. However, I don't know if this is a proper fix. If the ecommerce framework is supposed to be passing fully populated nodes to hook_feature_txn_workflow, then the actual bug may lie therein.

Patch attached. It is mostly comment, I only added one line of actual code.