### Environment

* Dubbo version: dubbo-registry-nacos 2.7.6
* Operating System version: Win10
* Java version: JAVA 8

### Steps to reproduce this issue
1 springboot  yml配置如下： 
registry:
     address: nacos://127.0.0.1:8848
     simplified: true
     group: dubbo-local
  metadata-report:
            address: nacos://127.0.0.1:8848
            group: dubbo-local

2 登陆nacos 1.2.1 控制台发现元数据 group配置生效，但是服务管理下的group依旧是DEFAULT_GROUP。

3 跟了下dubbo-registry-nacos 2.7.6的代码 发现在调用NamingService中 没有传入配置的group参数，使用的默认组参数 
 public void doRegister(URL url) {
        String serviceName = this.getServiceName(url);
        Instance instance = this.createInstance(url);
        this.execute((namingService) -> {
            namingService.registerInstance(serviceName, instance);
        });
    }

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

### Expected Result

What do you expected from the above steps？

### Actual Result

What actually happens?

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

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

return false;
        }
    }
    @Override
    public void doUnsubscribe(URL url, NotifyListener listener) {
        if (isAdminProtocol(url)) {
            shutdownServiceNamesLookup();
        }
    }
    private void shutdownServiceNamesLookup() {
        if (scheduledExecutorService != null) {
            scheduledExecutorService.shutdown();
        }
    }
    /**
     * Get the service names from the specified {@link URL url}
     *
     * @param url      {@link URL}
     * @param listener {@link NotifyListener}
     * @return non-null
     */
    private Set<String> getServiceNames(URL url, NotifyListener listener) {
        if (isAdminProtocol(url)) {
            scheduleServiceNamesLookup(url, listener);
            return getServiceNamesForOps(url);
        } else {
            return getServiceNames0(url);
        }
    }
    private Set<String> getServiceNames0(URL url) {