The periodic jobs for building images are all failing, add some
low-hanging fruits for fixing:
1) Remove usage of own Fedora image build tools, they were removed as
part of change Ie6a8496c202ff0bf330dd0f434cff8777e5ef112.
2) Add openstack/tripleo-image-elements and
openstack/heat-templates as required-repo for the build
jobs, they are requirements.
Still, these are still failing, let's disable the periodic jobs.
They have been broken since ages without fixing. There's no
record of a successful run under Zuul v3.
Last images at http://tarballs.openstack.org/magnum/images/ are from
2017.
Change-Id: I01122fa029b4124d912e80ea43bca07b8f2ebe5c
42c75c4d3d