FetchAllTopicList Error

Version：v2.1.2

```go
a, err := admin.NewAdmin(admin.WithResolver(primitive.NewPassthroughResolver(nameServerAddrs)))
if err != nil {
return nil, fmt.Errorf("new admin err:%s, addr:%v", err, nameServerAddrs)
}
res, err := a.FetchAllTopicList(ctx) //会报错
if err != nil {
return nil, err
}

a.CreateTopic(ctx, opts...) // 成功
```

当 namseServerAddrs 是 []string{ "http://docker.svc.cluster.local:9876" } 时，FetchAllTopicList 报错， CreateTopic 成功
当 namseServerAddrs 是 []string{ "127.0.0.1:9876" } 时，FetchAllTopicList 成功，CreateTopic 成功