tor/changes/ifaddrs-tests-network-configs

  o Minor fixes (unit tests, networking):
    - Make get_ifaddrs_* unit tests more tolerant of different network
      configurations:
        - Don't assume every test box has an IPv4 address.
        - Don't assume every test box has a non-localhost address.
    - Closes ticket #17255. Patch by "teor".
      Fix for unit tests released in 0.2.7.3.