enableKeepAlive kills all connections
```
$MyApp = new Server();

$Server = new Ratchet\WebSocket\WsServer(
    $MyApp
);

$app = new Ratchet\Http\HttpServer(
    $Server
);

$loop = React\EventLoop\Factory::create();

$websockets = new React\Socket\Server('0.0.0.0:1337', $loop);

$websockets_server = new Ratchet\Server\IoServer($app, $websockets, $loop);

$Server->enableKeepAlive($loop, 5);

$websockets_server->run();
```

When I have more than a certain number of clients, they are all disconnected every 25 seconds or so.
Am I using `enableKeepAlive` incorrectly?