[edpm_prepare] Fall back to quay.io bootc OS image

[rabi]

Default bootc OS images to quay.io/openstack-k8s-operators/edpm-bootc:latest-qcow2 when content-provider does not build them. CP output overrides that default.

[openshift-ci]

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[centosinfra-prod-github-app]

Build failed (check pipeline). Post recheck (without leading slash)
to rerun all jobs. Make sure the failure cause has been resolved before
you rerun jobs.

https://gateway-cloud-softwarefactory.apps.ocp.cloud.ci.centos.org/zuul/t/rdoproject.org/buildset/b3499b84fc204190bc1ab7ddfb1a469e

✔️ openstack-k8s-operators-content-provider SUCCESS in 2h 25m 01s
✔️ podified-multinode-edpm-deployment-crc SUCCESS in 1h 30m 11s
✔️ cifmw-crc-podified-edpm-baremetal SUCCESS in 1h 50m 38s
✔️ cifmw-crc-podified-edpm-baremetal-minor-update SUCCESS in 2h 10m 25s
✔️ cifmw-pod-zuul-files SUCCESS in 6m 25s
✔️ openstack-k8s-operators-content-provider-bootc SUCCESS in 1h 16m 55s
❌ cifmw-crc-podified-edpm-baremetal-bootc FAILURE in 40m 58s
❌ adoption-standalone-to-crc-ceph-provider FAILURE in 1h 15m 15s
✔️ noop SUCCESS in 0s
✔️ cifmw-pod-ansible-test SUCCESS in 9m 43s
✔️ cifmw-pod-pre-commit SUCCESS in 10m 18s
✔️ cifmw-molecule-edpm_prepare SUCCESS in 5m 44s

[rabi]

recheck