You can uninstall or removes an installed freeipa-admintools package itself from Ubuntu 16.04 LTS (Xenial Xerus) through the terminal,
$ sudo apt-get remove freeipa-admintools
If you would like to remove freeipa-admintools and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove freeipa-admintools
If you use with purge options to freeipa-admintools package all the configuration and dependent packages will be removed.
$ sudo apt-get purge freeipa-admintools
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 freeipa-admintools