Use kubeadm to standup etcd cluster

[alexbrand]

Currently, swizzle deploys etcd as a systemd service on etcd nodes. Instead, we should leverage kubeadm to bootstrap the etcd cluster.

Implementation:

• Ensure docker, kubeadm, kubelet are installed on etcd nodes
• Generate TLS assets using kubeadm
• Distribute TLS assets to all etcd nodes
• Generate static pod manifests

[johnharris85]

Do we want to give users the option here? Or just switch completely to using kubeadm for etcd standup? (fwiw I'm in favor of the latter)

[alexbrand]

I am in favor of completely switching, and that is what I was working on in #182. I ran into an issue, however, that prevent me from completing that PR.