Add TLS for etcd

[Ryan Hartje]

My initial attempts at enabling TLS for etcd failed:

etcd_1            | 2018-10-31 03:39:14.826572 I | embed: rejected connection from "192.168.16.3:58232" (error "tls: first record does not look like a TLS handshake", ServerName "")
etcd_1            | 2018-10-31 03:39:14.827667 I | embed: rejected connection from "192.168.16.3:58228" (error "tls: first record does not look like a TLS handshake", ServerName "")
etcd_1            | 2018-10-31 03:39:14.828648 I | embed: rejected connection from "192.168.16.3:58238" (error "tls: first record does not look like a TLS handshake", ServerName "")
etcd_1            | 2018-10-31 03:39:14.830291 I | embed: rejected connection from "192.168.16.3:58224" (error "tls: first record does not look like a TLS handshake", ServerName "")
etcd_1            | 2018-10-31 03:39:14.831818 I | embed: rejected connection from "192.168.16.3:58214" (error "tls: first record does not look like a TLS handshake", ServerName "")

I suspect I may not be properly generating certificates, which is done in bin/generate_certs.sh, but perhaps I misconfigured etcd.

In either case, we should enable TLS on etcd, and provide an example of using etcdctl securely.

[Ryan Hartje]

Closed by #3