On Debian 9 the copy of unit file `/etc/systemd/system/openvpn@.service` has no effect, see #583.
Same problem as #129 and #378, unit can not start on OpenVZ.
It must execute `systemctl enable` before `systemctl restart`.
So the new link to `/etc/systemd/system/openvpn@.service` was created before `systemctl restart`.
Fix https://github.com/angristan/openvpn-install/issues/583
For faster reconnects with UDP is better to send the the explicit-exit-notify to server. With this the server can directly see, that the client will exit.