o Minor bugfixes (logging):
    - Avoid a spurious log message about missing subprotocol versions, when
      the consensus that we're reading from is older than the current
      release. .  Previously we had made this message nonfatal in this case,
      but in practice, it is never relevant when the consensus is older than
      the current release.  Fixes bug 40281; bugfix on 0.4.0.1-alpha.