* Update cluster health check command for newer etcd
Existing docs assume the older (v3.2) etcdctl `health-check` command but with a 3.4.3 cluster (which is what kubeadm creates in the static manifest now), that subcommand is no longer supported and returns 404 errors like:
```
root@etcd-1:~# docker run --rm -it --net host -v /etc/kubernetes:/etc/kubernetes quay.io/coreos/etcd:${ETCD_TAG} etcdctl --cert-file /etc/kubernetes/pki/etcd/peer.crt --key-file /etc/kubernetes/pki/etcd/peer.key --ca-file /etc/kubernetes/pki/etcd/ca.crt --endpoints https://10.170.68.181:2379 cluster-health
cluster may be unhealthy: failed to list members
Error: unexpected status code 404
```
* PR review changes
Eric Smalling
70936d4dbd