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