- [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!
```

String address = ConfigUtils.getProperty("dubbo.registry.address");
            if (address != null && address.length() > 0) {
                List<RegistryConfig> tmpRegistries = new ArrayList<RegistryConfig>();
                String[] as = address.split("\\s*[|]+\\s*");
                for (String a : as) {
                    RegistryConfig registryConfig = new RegistryConfig();
                    registryConfig.setAddress(a);
                    registryConfig.refresh();
                    tmpRegistries.add(registryConfig);
                }
                setRegistries(tmpRegistries);
            }
        }
    }
    /**
     * For compatibility purpose, use registry as the default config center if the registry protocol is zookeeper and
     * there's no config center specified explicitly.
     */
    private void useRegistryForConfigIfNecessary() {
        registries.stream().filter(RegistryConfig::isZookeeperProtocol).findFirst().ifPresent(rc -> {
            // 
            Environment.getInstance().getDynamicConfiguration().orElseGet(() -> {
                ConfigManager configManager = ConfigManager.getInstance();
                ConfigCenterConfig cc = configManager.getConfigCenter().orElse(new ConfigCenterConfig());
                cc.setProtocol(rc.getProtocol());
                cc.setAddress(rc.getAddress());
                cc.setHighestPriority(false);
                setConfigCenter(cc);
                startConfigCenter();
                return null;