问题描述：NacosMetadataReport#getServiceAppMapping 方法将监听器存入casListenerMap中，key是使用 DEFAULT_MAPPING_GROUP
作为group构建；但是 NacosMetadataReport#removeServiceAppMappingListener方法中，移除监听器时使用group不是 DEFAULT_MAPPING_GROUP，从而导致无法正常移除监听器

~~~
@Override
    public Set<String> getServiceAppMapping(String serviceKey, MappingListener listener, URL url) {
        String group = DEFAULT_MAPPING_GROUP;

        if (null == casListenerMap.get(buildListenerKey(serviceKey, group))) {
            addCasServiceMappingListener(serviceKey, group, listener);
        }
        String content = getConfig(serviceKey, group);
        return ServiceNameMapping.getAppNames(content);
    }

    @Override
    public void removeServiceAppMappingListener(String serviceKey, MappingListener listener) {
        MappingDataListener mappingDataListener = casListenerMap.get(buildListenerKey(serviceKey, group));
        if (null != mappingDataListener) {
            removeCasServiceMappingListener(serviceKey, group, listener);
        }
    }
~~~
logger.error(e.getErrMsg(), e);
            }
            throw new IllegalStateException(e);
        }
        return configService;
    }
    private Properties buildNacosProperties(URL url) {
        Properties properties = new Properties();
        setServerAddr(url, properties);
        setProperties(url, properties);
        return properties;
    }
    private void setServerAddr(URL url, Properties properties) {
        StringBuilder serverAddrBuilder =
                new StringBuilder(url.getHost()) 
                        .append(':')
                        .append(url.getPort()); 
        
        String backup = url.getParameter(BACKUP_KEY);
        if (backup != null) {
            serverAddrBuilder.append(',').append(backup);
        }
        String serverAddr = serverAddrBuilder.toString();
        properties.put(SERVER_ADDR, serverAddr);
    }
    private static void setProperties(URL url, Properties properties) {
        
        Map<String, String> parameters = url.getParameters(of(PropertyKeyConst.class));
        
        properties.putAll(parameters);