o Minor bugfixes:
    - Clear the table recording the time of the last request for each
      hidden service descriptor from each HS directory on SIGNAL
      NEWNYM.  Previously, we would clear our HS descriptor cache on
      SIGNAL NEWNYM, but if we had previously retrieved a descriptor
      (or tried to) from every directory responsible for it, we would
      refuse to fetch it again for up to 15 minutes.  Bugfix on
      0.2.2.25-alpha; fixes bug 3309.