jursonmo

fix: the selector doesn't work without Discovery

2

#### Description (what this PR does / why we need it): the selector doesn't work without Discovery: (transport/http): when create http client with WithSelector() without WithDiscovery(), the selector doesn't work...

```go myselector := = wrr.New() ...... myselector.Apply(nodes) client, err := http.NewClient(context.Background(), WithSelector(myselector)) client.Do(req) // selector does't work? ``` maybe the problem is here: https://github.com/go-kratos/kratos/blob/70317d05a07a6382a1a18f14464771808c789e0c/transport/http/client.go#L272 should be : ```go //if client.r...