This should mitigate a hypothetical compromise of the scripts used to
manage the CA and other sensitive material.
The examples should still work and make sense although I have not tried
all of them with this change applied.
Note that I did not append the --net=none to all examples because in
some cases network is probably wanted.
* Changing this for all docs was not accepted by @kylemanna.
https://github.com/kylemanna/docker-openvpn/pull/65#issuecomment-138559257
