[Bug] I can not get metrics from store server

### Bug Type (问题类型)

rest-api (结果不合预期)

### Before submit

- [X] 我已经确认现有的 [Issues](https://github.com/apache/hugegraph/issues) 与 [FAQ](https://hugegraph.apache.org/docs/guides/faq/) 中没有相同 / 重复问题 (I have confirmed and searched that there are no similar problems in the historical issue and documents)

### Environment (环境信息)

- Server Version: master branch
- Backend: Server deployed by [Guide doc](https://github.com/apache/incubator-hugegraph/wiki/HugeGraph-Distributed-(pd%E2%80%90store)-Version-Deployment-Guide)
- OS: Mac
- Data Size: Less than 10 vertices

### Expected & Actual behavior (期望与实际表现)
If I call
```curl "http://localhost:8520/metrics"```
It just return ```{}```.
No metrics are returned.

But call
```
curl "http://localhost:8520/metrics/drive"
```
It can return ```
{"/":{"usable_space":89916,"total_space":471482,"free_space":89916,"size_unit":"MB"}}%```

### Vertex/Edge example (问题点 / 边数据举例)

_No response_

### Schema [VertexLabel, EdgeLabel, IndexLabel] (元数据结构)

_No response_