[IMP] website_sale : avoid duplicated order lines

Add line id to while calling _cart_update() from sale_get_order()
The missing line_id parametre was making the _cart_find_product_line() call to fail as it was linked to an option while searching for lines without options (making the method recreate new lines).
Fixes #2573

addons/website_sale/models/sale_order.py

@@ -193,7 +193,7 @@ class website(orm.Model):
                 values.update(sale_order.onchange_pricelist_id(pricelist_id, None)['value'])
                 sale_order.write(values)
                 for line in sale_order.order_line:
-                    sale_order._cart_update(product_id=line.product_id.id, add_qty=0)
+                    sale_order._cart_update(product_id=line.product_id.id, line_id=line.id, add_qty=0)
 
             # update browse record
             if (code and code != sale_order.pricelist_id.code) or sale_order.partner_id.id !=  partner.id: