@Override
    public Thread newThread(Runnable runnable) {
        Thread t = defaultThreadFactory.newThread(runnable);
        t.setDaemon(true);
        if (prefix != null) {
            t.setName(prefix + t.getName());
        }
        return t;
    }
Creates a deamon thread factory that creates threads with the default names
provided by <code>Executors.defaultThreadFactory()</code> prepended by the
specified prefix.

@param prefix the thread name prefix to use
vespajlib/src/main/java/com/yahoo/concurrent/DaemonThreadFactory.java