You can uninstall or removes an installed l2tpd package itself from Debian 8 (Jessie) through the terminal,
$ sudo apt-get remove l2tpd
If you would like to remove l2tpd and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove l2tpd
If you use with purge options to l2tpd package all the configuration and dependent packages will be removed.
$ sudo apt-get purge l2tpd
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove l2tpd