Remove ignored do_request timeout argument

The timeout to the underlying request was always self._request_timeout,
regardless of the value of the do_request(timeout) arg provided.  Both
callers always pass timeout=self._request_timeout anyway, so just remove
this unused/misleading argument.

Change-Id: I911ee986caef8fcf9b97ef622a03856d4351bee0
Merge "Remove ignored do_request timeout argument"