[SW-2503] Tried using port 54321 for Flow proxy, but port was already occupied

[dzlab]

Updated ProxyStarter.scala. so that when tries to bind on a port it uses the address 0.0.0.0

The problem description: #2414

[mn-mikke]

LGTM

[Pscheidl]

This is already used for the Jetty to start anyway, so checking all local interfaces is more appropriate anyway.

See SparklingWaterJettyHelper.scala class.

  def startServer(port: Int): Server = {
    val jettyServer = createJettyServer("0.0.0.0", port)
    val context = createServletContextHandler()
    if (h2oHttpView.getConfig.loginType != LoginType.NONE) {
      context.setSecurityHandler(authWrapper(jettyServer).asInstanceOf[SecurityHandler])
    }
    jettyServer.setHandler(context)
    jettyServer.start()
    jettyServer
  }

[mn-mikke]

@dzlab Thanks for you contribution! Merging...