Authentication failure on all backends does not immediately close sessions

Currently only ER_ACCESS_DENIED_ERROR (1045) is handled as an authentication failure and ER_DBACCESS_DENIED_ERROR (1044) is not. This means that if authentication fails due to DB access, a user database refresh is not triggered. Additionally, readwritesplit does not close the connection immediately when the all of the backends fail but only when the next query arrives. The expected behavior is that the session is closed as soon as all backends have failed with an authentication related error.