tor/changes/log_heartbeat_test

  o Minor bugfix (testing):
    - The test for log_heartbeat was incorrectly failing in timezones
      with non-integer offsets. Instead of comparing the end of the
      time string against a constant, compare it to the output of
      format_local_iso_time when given the correct input.
      Fixes bug 18039; bugfix on 0.2.5.4-alpha.