Further improvements to Ruby HTTP server

  * Server should always find a free port now.
  * Clearer defined states in operation.
    - Stop listening on the socket past 1024 as payload should have
      been delivered by that point.
    - If the payload is <1024 bytes then *assume* it is a good
      request and send the kickstart file.
    - Anything else, assume is a 500.
  * Accepts a different name for the kickstart file.
Use Vagrant's Ruby else system Ruby else fail