[FIX] delivery: Get correct carrier price on picking created from SO

Steps to reproduce:

* Create a sales order (SO).
* Assign a carrier.
* Don't press on "Set price" button next to carrier.
* Validate SO.
* Validate picking.
* Delivery line is added to the SO with price 0.

This is because the delivery SO line is added with the value of
picking carrier_price field, but that field hasn't been set.
If you modify on view carrier field, there's an onchange that
fills correct price, so I use that onchange method for getting
same results.

addons/delivery/models/stock_move.py

@@ -38,4 +38,7 @@ class StockMove(models.Model):
                 pickings.write({
                     'carrier_id': proc.sale_line_id.order_id.carrier_id.id,
                 })
+                # Get correct carrier price
+                for picking in pickings:
+                    picking.onchange_carrier()
         return res