Restore preferIPv4Stack value on Forge 1.8

@Mod.EventHandler
public void forgePreInitialization(FMLPreInitializationEvent event)
{
    String preferIPv4Stack = System.getProperty("java.net.preferIPv4Stack");
    if((preferIPv4Stack != null) && (preferIPv4Stack.equals("true")))
    {
        System.err.println("WARNING: `java.net.preferIPv4Stack' was true. Check for original JVM arguments...");
        System.setProperty("java.net.preferIPv4Stack", "false");

        RuntimeMXBean runtimeMxBean = ManagementFactory.getRuntimeMXBean();
        List<String> arguments = runtimeMxBean.getInputArguments();
        for(String arg : arguments)
        {
            int at = arg.indexOf("-Djava.net.preferIPv4Stack=");
            if(at >= 0)
            {
                System.setProperty("java.net.preferIPv4Stack", arg.substring(at + 27));
                break;
            }
        }

        System.err.println("Restored original `java.net.preferIPv4Stack'. Goodluck!");
    }
}