Suppress shutdown error message

I investigated the possibility of preventing the IllegalStateException during shutdown of the SingleNodeApplication, but this happens before we get into SmartLifecycle.stop() in EmbeddedZooKeeper, so not obvious what can be done. Of course this suppresses all log messages from PathChildrenCache, which currently is only done in one place. 

````
protected void handleException(Throwable e)
{
    log.error("", e);
}
````