Hello,

I've just updated to elasticsearch version 6.3.0 and seems that rest high level client doesn't work there as has to.
Right now I am using the next code to refresh indexes:
```
Settings settings = Settings.builder()
        .put("client.transport.sniff", true)
        .put("cluster.name", "myTestCluster")
        .build();

System.setProperty("es.set.netty.runtime.available.processors", "false");

TransportClient client = new PreBuiltTransportClient(settings);
client.addTransportAddress(new TransportAddress(InetAddress.getByName("192.168.56.50"), 9300));
```

And then use the next method to refresh indices:
`transportClient.admin().indices().prepareRefresh().get()`

Now, I would like to update my client to use REST High Level Client. I've changed my code to:
```
System.setProperty("es.set.netty.runtime.available.processors", "false");

RestClientBuilder restClientBuilder = RestClient.builder(new HttpHost("192.168.56.50", 9200, "http"));
restClientBuilder.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
    @Override
    public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder requestConfigBuilder) {
        return requestConfigBuilder.setConnectTimeout(60000).setSocketTimeout(60000)
                .setConnectionRequestTimeout(0);
    }
});
restClientBuilder.setMaxRetryTimeoutMillis(60000);
RestHighLevelClient client = new RestHighLevelClient(restClientBuilder);
```
And now I try to refresh indices with the next code:
`client.indices().refresh(new RefreshRequest());`

Unfortunately I am getting an error when I am trying to refresh indices:
```
java.io.IOException: listener timeout after waiting for [60000] ms
        at org.elasticsearch.client.RestClient$SyncResponseListener.get(RestClient.java:684)
...
```
Here is the full log: http://paste.openstack.org/show/723460/

Here is my gradle dependencies:
```
compile "org.elasticsearch:elasticsearch:6.3.0"
compile "org.elasticsearch.client:elasticsearch-rest-high-level-client:6.3.0"
compile "org.elasticsearch.client:elasticsearch-rest-client:6.3.0"
compile "org.elasticsearch.client:transport:6.3.0"
```

Does anyone know why is it happening? My elasticsearch 6.3.0 is running under virtual machine. All ports are open. I can perform requests by using `curl` to port 9200 but REST High Level Client doesn't work.

Best regards

---
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