  o Minor bugfix (relay address resolution):
    - Avoid unnecessary calls to directory_fetches_from_authorities()
      on relays. This avoids spurious address resolutions and
      descriptor rebuilds. This is a mitigation for 21789. The original
      bug was introduced in commit 35bbf2e as part of prop210.
      Fixes 23470 in 0.2.8.1-alpha.
