o Major bugfixes:
    - When generating a vote with keypinning disabled, never include two
      entries for the same ed25519 identity.  This bug was causing
      authorities to generate votes that they could not parse when a router
      violated key pinning by changing its RSA identity but keeping its
      Ed25519 identity.  Fixes bug 17668; fixes part of bug 18318.  Bugfix on
      0.2.7.2-alpha.