- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.2
* Operating System version: macOS 10.12.6
* Java version: 1.8

### Steps to reproduce this issue



Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

```java

    ZookeeperDynamicConfiguration(URL url, ZookeeperTransporter zookeeperTransporter) {
        this.url = url;
        rootPath = "/" + url.getParameter(CONFIG_NAMESPACE_KEY, DEFAULT_GROUP) + "/config";

        initializedLatch = new CountDownLatch(1);
        this.cacheListener = new CacheListener(rootPath, initializedLatch);
        this.executor = Executors.newFixedThreadPool(1, new NamedThreadFactory(this.getClass().getSimpleName(), true));

        zkClient = zookeeperTransporter.connect(url);
        zkClient.addDataListener(rootPath, cacheListener, executor);
        try {
            // Wait for connection
            this.initializedLatch.await();
        } catch (InterruptedException e) {
            logger.warn("Failed to build local cache for config center (zookeeper)." + url);
        }
    }
```

`        zkClient = zookeeperTransporter.connect(url);`会通过URL中的client参数来正确选择自适应扩展来初始化zk客户端。但在初始化配置中心的时候，URL是由ConfigCenterConfig得到的，此时URL中无client的信息，所以这个地方创建zk还是用的默认的zkClient。希望和注册中心时候一样获取自己扩展的zkClient


### Actual Result

What actually happens?

If there is an exception, please attach the exception trace:

```
Just put your stack trace here!
```

return UrlUtils.parseURL(address, map);
        } else if (REGISTRY_PROTOCOL.equals(monitor.getProtocol()) && registryURL != null) {
            return URLBuilder.from(registryURL)
                    .setProtocol(DUBBO_PROTOCOL)
                    .addParameter(PROTOCOL_KEY, REGISTRY_PROTOCOL)
                    .addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map))
                    .build();
        }
        return null;
    }
    static void appendRuntimeParameters(Map<String, String> map) {
        map.put(DUBBO_VERSION_KEY, Version.getProtocolVersion());
        map.put(RELEASE_KEY, Version.getVersion());
        map.put(TIMESTAMP_KEY, String.valueOf(System.currentTimeMillis()));
        if (ConfigUtils.getPid() > 0) {
            map.put(PID_KEY, String.valueOf(ConfigUtils.getPid()));
        }
    }
    private URL loadMetadataReporterURL() {
        String address = metadataReportConfig.getAddress();
        if (StringUtils.isEmpty(address)) {
            return null;
        }
        Map<String, String> map = new HashMap<String, String>();
        appendParameters(map, metadataReportConfig);
        return UrlUtils.parseURL(address, map);
    }
    protected MetadataReportService getMetadataReportService() {
        if (metadataReportConfig == null || !metadataReportConfig.isValid()) {
            return null;