[FIX] account: product variants prices in invoices

when a customer invoice is created directly,
if a product variant is selected,
it now computes the price from the product variant and
not from the product template.

opw: 629285

addons/account/account_invoice.py

@@ -1349,7 +1349,7 @@ class account_invoice_line(models.Model):
         if type in ('in_invoice', 'in_refund'):
             values['price_unit'] = price_unit or product.standard_price
         else:
-            values['price_unit'] = product.list_price
+            values['price_unit'] = product.lst_price
 
         values['uos_id'] = uom_id or product.uom_id.id
         domain = {'uos_id': [('category_id', '=', product.uom_id.category_id.id)]}