openvpn-easy-rsa: update to 3.0.1

openvpn-easy-rsa: update to 3.0.1

easy-rsa v3 is now a single script. It expects a 'vars'
configuration file which path can be set using easy-rsa
options, environment variables or just looking in the
current directory.

The default usage would be:

 # cd /etc/easy-rsa
 # easy-rsa COMMAND [command-options]

Following upstream changes, /etc/easy-rsa/pki replaces
/etc/easy-rsa/keys directory.

The default /etc/easy-rsa/pki dir is marked to be kept during
upgrade (WARN: priv keys are saved in the system backup)
/etc/easy-rsa/openssl.1.0.cnf is now marked as config file while
index and serial got removed.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>