cephadm-preflight: only use $basearch for IBM yum repo (backport #211)

[mergify]

This is an automatic backport of pull request #211 done by Mergify.
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[ktdreyer]

@andrewschoen would you mind resolving the conflicts here and force-pushing to mergify/bp/pacific/pr-211?

I think we should functionally test this before you tag v1.14.0, just to make sure everything's working as we expect. For example, I have questions about #207 I've never seen a $ character in a repository's name before.

[andrewschoen]

@ktdreyer I would agree on some additional testing. There is some functional testing with this job, I'm not sure what all it covers though. https://2.jenkins.ceph.com/job/cephadm-ansible-prs-el8-functional/243/

[andrewschoen]

From those tests it doesn't look like $basearch is expanding into anything, it's being treated as a string.

changed: [ceph-node0] => (item=$basearch) => changed=true 
  ansible_loop_var: item
  attempts: 1
  item: $basearch
  repo: ceph_stable_$basearch
  state: present

[andrewschoen]

Later on it does expand though, you can see here from the ceph-common installation.

  ceph-common             x86_64  2:16.2.11-0.el8                      ceph_stable_x86_64   24 M