Execute transition callbacks in promos

I noticed in the core copy of Spree::OrdersController#update we execute transition callbacks:
https://github.com/spree/spree/blob/1-3-stable/core/app/controllers/spree/orders_controller.rb#L29

But in the promo copy of Spree::OrdersController#update we do not:
https://github.com/spree/spree/blob/1-3-stable/promo/app/controllers/spree/orders_controller_decorator.rb#L18

This PR fixes that, although, I'm wondering why we define these methods twice at all?