Fixes #5761, #5899 - Update Katello kickstarts

This change brings the Katello kickstarts forward to match what's in the
Foreman community versions, with the community yum repos removed as Katello
will manage content.

This includes the security hardening in #5895, and Realm integration from
Merge pull request #4240 from stbenjam/5761-realm-template

fixes #5761, #5899 - Update Katello kickstarts