Resolves race condition in ScriptStatusServer random port assignment

If a random port is requested, the ScriptStatusServer binds a server socket, grabs resulting port, disconnects the socket, and passes this port number over to Jetty to start up on. This constituted an unnecessary race condition. If you give Jetty port zero, it'll bind to a random port on its own. The trouble was how to grab and log the bound port so the user could get to it. This patch manages to do it.

Tested with the `demo/demo.pig` script after `mvn package`.