- [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: 3.0.0


### Steps to reproduce this issue

1. dubbo config-center 相关yml配置如下
```
dubbo:
  ...
  config-center:
    address: nacos://xxxx:8848
    username: someusername
    password: xxxx
```

2. 在执行 org.apache.dubbo.config.bootstrap.DubboBootstrap#startConfigCenter 方法时会调用 configCenterConfig.refresh(); 方法。
3. setAddress方法，会覆盖已经设置过的username和password

```
public void setAddress(String address) {
        this.address = address;
        if (address != null) {
            try {
                URL url = URL.valueOf(address);
                setUsername(url.getUsername());
                setPassword(url.getPassword());
                updateIdIfAbsent(url.getProtocol());
                updateProtocolIfAbsent(url.getProtocol());
                updatePortIfAbsent(url.getPort());
                updateParameters(url.getParameters());
            } catch (Exception ignored) {
            }
        }
    }
```

### Expected Result

希望设置前先判断是否已经设置过相关属性值



map.put(PROTOCOL_KEY, ZOOKEEPER_PROTOCOL);
        }
        return UrlUtils.parseURL(address, map);
    }
    public boolean checkOrUpdateInited() {
        return inited.compareAndSet(false, true);
    }
    public Map<String, String> getExternalConfiguration() {
        return externalConfiguration;
    }
    public Map<String, String> getAppExternalConfiguration() {
        return appExternalConfiguration;
    }
    public void setExternalConfig(Map<String, String> externalConfiguration) {
        this.externalConfiguration = externalConfiguration;
    }
    public void setAppExternalConfig(Map<String, String> appExternalConfiguration) {
        this.appExternalConfiguration = appExternalConfiguration;
    }
    public String getProtocol() {
        return protocol;
    }
    public void setProtocol(String protocol) {
        this.protocol = protocol;
    }
    @Parameter(excluded = true)
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {