Auto-port calling listen callback N times where N is the amount of port attempts

[Marak]

There is an issue with the auto-port functionality which causes the callback handler for http.listen to be called N times, where N is the attempts at auto-porting.

The core issue is that either Node itself or Express won't pass EADDRINUSE errors through the normal error object in listen callback. The only way to catch this error is to listen for server.on("error").

Work around requires minor refactor of auto-port logic.