Remove 20-openvpn CARP script unless OpenVPN is actually being used

[nzkiwi68]

Have a master "Enable OpenVPN" that writes the 20-openvpn script into /usr/local/etc/rc.syshook.d/carp/ directory, otherwise the script does not exist.

If you unselect "OpenVPN" then the CARP script /usr/local/etc/rc.syshook.d/carp/20-openvpn is removed.

Why?
Because the script gets called and runs again and again and again for CARP events of INIT, BACKUP and MASTER events even when your are not running OpenVPN.