test: revocation: Minor style clean ups
test: revocation: Minor style clean ups

* Always tear down test server if it exits for any reason.
* Give container + volume unique name.
* Drop iptables commands, these scare me as they are mucking with the
  state of my machine.
* Fix path to cert revocation list, the OpenVPN crl is copied at
  start-up and is a race condition.

kylemanna/docker-openvpn