fixes #6853 - make host group provisioning work with katello

Needs ~~https://github.com/theforeman/foreman/pull/1634~~, https://github.com/theforeman/foreman/pull/1636, https://github.com/theforeman/community-templates/pull/97, https://github.com/theforeman/foreman/pull/1637
@daviddavis Same place we do it for Host.