EasyRSA 3.0.7 introduces a check for the existence of vars in the
vars_setup() function. '$ easyrsa init-pki' fails without first
creating the file. See https://github.com/OpenVPN/easy-rsa/commit/
abaa2f57b48e218ac58ee6dc793f178aada31f82#diff-231cb43897d7aa2a98df
da5720c2b40f for the exact change.

* This would hang the tests.

* EasyRSA moves the files aside now, see EasyRSA v3.0.6 for details
* OpenVPN/easy-rsa@675fc99

* 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.

* The iptables rule to check will only be present after the server has
  succeeded at starting-up.
* Spin up to ~10 seconds waiting.
* Fix eval which was intended to be an exec.
* Simplify kill + rm.

* Don't muck with iptables on the host machine.

* Don't muck with iptables on the host machine.

* Don't muck with iptables on the host machine.

Fix build and tests

* Results in a slightly simpler docker image.

* Clean-up processes properly.

* Instead encourage the user to change how they invoke docker.

* It's fine for these to fail, it's expected.

* Fix all the test to not require this flag.

* Fix all the docs to not mention this flag.

* This is really hard to work on other things while running this test
  when the host networking stack is being manipulated, primarily the
  default route.
* Propagate DEBUG flag deeper where possible.

Cleanup some tests and documentation

* This is overly verbose.

* This exists to import/export a number of easy-rsa default values but
  creates headaches for old volumes due to changes where easy-rsa
  insists on loading the var file if the environment variable is set.
* Going forward people should pass the variables via:
    `docker run -e EASYRSA_var ...`
* Closes #608

Fix /etc/openvpn/vars bug for old docker volumes