Update taxes only for draft invoices

invoice.py

@@ -920,9 +920,12 @@ class Invoice(ModelWorkflow, ModelSQL, ModelView):
                 keys.remove(key)
         if len(keys):
             self.check_modify(cursor, user, ids, context=context)
+        update_tax_ids = [x.id for x in self.browse(cursor, user, ids,
+            context=context) if x.state == 'draft']
         res = super(Invoice, self).write(cursor, user, ids, vals,
                 context=context)
-        self.update_taxes(cursor, user, ids, context=context)
+        if update_tax_ids:
+            self.update_taxes(cursor, user, update_tax_ids, context=context)
         if 'state' in vals and vals['state'] in ('paid', 'cancel'):
             self.workflow_trigger_trigger(cursor, user, ids, context=context)
         return res