Redis endpoints success/error/timeout stats are zero

*Title*: Redis endpoints success/error/timeout stats are zero

*Description*:
There is new feature in v1.29.0 - [per_endpoint_stats](https://github.com/envoyproxy/envoy/pull/29709).
I've enabled it with redis upstreams and see `envoy_cluster_endpoint_rq_total` increasing, but `envoy_cluster_endpoint_rq_success`, `envoy_cluster_endpoint_rq_error` and `envoy_cluster_endpoint_rq_timeout` are always zero.
`/clusters` endpoint also shows zero values for these stats.

We're currently using envoy only with redis upstreams, so I don't know if is only redis related or not.

>What issue is being seen? Describe what should be happening instead of

`envoy_cluster_endpoint_rq_success`, `envoy_cluster_endpoint_rq_error` and `envoy_cluster_endpoint_rq_timeout` counters increasing accordingly.

*Repro steps*:
Enable in cluster with redis upstreams:
```
track_cluster_stats:
per_endpoint_stats: true
```
Make some requests.
Observe only `envoy_cluster_endpoint_rq_total` increasing, but not the other rq stats.

*Admin and Stats Output*:
/stats: https://gist.github.com/zigmund/642b32394ba87612188e9eff73c605b1
/clusters: https://gist.github.com/zigmund/9eec9c17e933fa52299539dede1f8be5
/routes: `404 Not Found`
/server_info: https://gist.github.com/zigmund/df51bd50b7a9267c7a4b2ac82712e70c

*Config*:
https://gist.github.com/zigmund/b0194f01acb427933f8c7e9d8b3b9720

*Logs*:
https://gist.github.com/zigmund/62063e1dff35af0afff585ea481c04cc