genconfig: Fix typo, use Docker for port mapping

* Use docker run ... -p 1337:1194/udp kylemanna/openvpn
genconfig: Handle "-r 0" to disable extra routes

* Disable extra routes for minimal VPNs.
Dockerfile: Set WORKDIR to /etc/openvpn

* Set WORKDIR to simply admin when I run cmd `bash`
* Add comment on port