[FIX] website_sale: recompute fiscal position

Following commit 6006c0d72a, the shipping address can be changed after
the call to `checkout_form_save`. This is the case, for example, when
the user has the same shipping and invoicing address. We need to make
sure to recompute the fiscal position after the shipping address is
finally set.

opw-689281

addons/website_sale/controllers/main.py

@@ -644,9 +644,6 @@ class website_sale(http.Controller):
         if checkout.get('shipping_id'):
             order.write({'partner_shipping_id': checkout['shipping_id']})
 
-        order_obj.onchange_partner_shipping_id(cr, SUPERUSER_ID, [order.id], context=context)
-        order.order_line._compute_tax_id()
-
         order_info = {
             'message_partner_ids': [(4, partner_id), (3, request.website.partner_id.id)],
         }
@@ -689,6 +686,9 @@ class website_sale(http.Controller):
         if not int(post.get('shipping_id', 0)):
             order.partner_shipping_id = order.partner_invoice_id
 
+        order.onchange_partner_shipping_id()
+        order.order_line._compute_tax_id()
+
         request.session['sale_last_order_id'] = order.id
 
         request.website.sale_get_order(update_pricelist=True, context=context)