testnode: No pkg tasks before repos are set up

testnode: No pkg tasks before repos are set up

Newer versions of RHEL8 don't like having yum called if they don't have repos setup.

When a RHEL8 machine gets provisioned via Cobbler, we zap the disks before we register the server to Satellite (or CDN).

We don't really need to check if gdisk and device-mapper are installed during a Cobbler install because we know they're installed in https://github.com/ceph/ceph-cm-ansible/blob/main/roles/cobbler/templates/snippets/cephlab_packages_rhel

Signed-off-by: David Galloway <dgallowa@redhat.com>