o Major bugfixes (bootstrap):
    - Check if bootstrap consensus downloads are still needed
      when the linked connection attaches. This prevents tor
      making unnecessary begindir-style connections, which are
      the only directory connections tor clients make since
      #18483 was merged.
    - Fix some edge cases where consensus download connections
      may not have been closed, even though they were not needed.
    - Make relays retry consensus downloads the correct number of
      times, rather than the more aggressive client retry count.
    - Stop downloading consensuses when we have a consensus,
      even if we don't have all the certificates for it yet.
      Closes ticket 18943, bugfix on #4483 in 0.2.8.1-alpha,
      patches by arma and teor.