You can uninstall or removes an installed libownet-2.8-15 package itself from Ubuntu 14.04 LTS (Trusty Tahr) through the terminal,
$ sudo apt-get remove libownet-2.8-15
If you would like to remove libownet-2.8-15 and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove libownet-2.8-15
If you use with purge options to libownet-2.8-15 package all the configuration and dependent packages will be removed.
$ sudo apt-get purge libownet-2.8-15
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 libownet-2.8-15