Instruction errors in `Run etcd clusters inside containers`

In https://etcd.io/docs/v3.4/op-guide/container/#running-a-3-node-etcd-cluster-1

1. `latest` tag of `gcr.io/etcd-development/etcd` is 3.3.12 and `quay.io` even more outdated that uploaded three years ago. I guess the authority is on your side so if would be great if you could update the `latest` tag to the correct version. Ref: [gcloud](https://console.cloud.google.com/gcr/images/etcd-development/GLOBAL/etcd?gcrImageListsize=30&gcrImageListquery=%255B%257B_22k_22_3A_22_22_2C_22t_22_3A10_2C_22v_22_3A_22_5C_22latest_5C_22_22%257D%255D) and [quay](https://quay.io/repository/coreos/etcd?tag=latest&tab=tags)
2. all three etcd nodes in docker have the same name `etcd` so the cluster could not be built. Might change to name to `${THIS_NAME}`

```
docker run \
-p 2379:2379 \
-p 2380:2380 \
--volume=${DATA_DIR}:/etcd-data \
--name etcd ${REGISTRY}:${ETCD_VERSION} \
...
```
3. use detached mode when `docker run`, or the rest commands could not be accessed.