o Major bugfixes (performance):
    - Do not recompute whether we have sufficient information to build
      circuits every time we make a successful connection. Previously,
      we would forget our cached value for this flag every time we
      successfully opened a channel (or marked a router as running or not
      running for any
      other reason), regardless of whether we had
      previously believed the router to be running. This forced us to
      run a fairly expensive update operation with relatively
      high frequency.
      Fixes bug 12170; bugfix on 0.1.2.1-alpha.