[FIX] website_sale_delivery: reset carrier on cart update
[FIX] website_sale_delivery: reset carrier on cart update

It makes no sense to recompute delivery costs at each update of the cart;
furthermore, it prevents users that already selected a carrier to remove
the last products of their carts

This fix is additional to e4e1e571c2e5854b16b913b9b7bce9774b395055

Elico-Corp/odoo_OCB,storm-computers/odoo,bplancher/odoo,dfang/odoo,microcom/odoo,dfang/odoo,ygol/odoo,storm-computers/odoo,bplancher/odoo,laslabs/odoo,microcom/odoo,laslabs/odoo,hip-odoo/odoo,microcom/odoo,Elico-Corp/odoo_OCB,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo,laslabs/odoo,dfang/odoo,laslabs/odoo,bplancher/odoo,dfang/odoo,microcom/odoo,storm-computers/odoo,Elico-Corp/odoo_OCB,dfang/odoo,ygol/odoo,ygol/odoo,Elico-Corp/odoo_OCB,bplancher/odoo,ygol/odoo,hip-odoo/odoo,laslabs/odoo,ygol/odoo,storm-computers/odoo,hip-odoo/odoo,microcom/odoo,ygol/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,microcom/odoo,dfang/odoo,laslabs/odoo,bplancher/odoo,storm-computers/odoo,storm-computers/odoo,hip-odoo/odoo,bplancher/odoo