### 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!
```

if (serviceName != null && serviceName.startsWith(prefix)) {
                            accepted = true;
                            break;
                        }
                    }
                    return accepted;
                });
                doSubscribe(url, listener, serviceNames);
            }, LOOKUP_INTERVAL, LOOKUP_INTERVAL, TimeUnit.SECONDS);
        }
    }
    /**
     * Get the service names for Dubbo OPS
     *
     * @param url {@link URL}
     * @return non-null
     */
    private Set<String> getServiceNamesForOps(URL url) {
        Set<String> serviceNames = getAllServiceNames();
        filterServiceNames(serviceNames, url);
        return serviceNames;
    }
    private Set<String> getAllServiceNames() {
        final Set<String> serviceNames = new LinkedHashSet<>();
        execute(namingService -> {
            int pageIndex = 1;
            ListView<String> listView = namingService.getServicesOfServer(pageIndex, PAGINATION_SIZE);
            
            List<String> firstPageData = listView.getData();