vpn: l2tp: T3009: fix non effective "authentication require" option
vpn: l2tp: T3009: fix non effective "authentication require" option

The CLI node was read in incorrect (wrong path). In addtition the list was not
reset to [] when authentication was specified on the CLI.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x