Dont advance order state when adding an item to cart

As of d02f67dbbf7e8ae1f61b65066c2a3a8234796a11

Admin would click to add a item to the order which would create the line
item and shipment but because we advance the order to address state the
shipments would be destroyed Order#ensure_available_shipping_rates

Cant see why we needed advance order in the first place.
Add completed back as default state.