Stop using EOL Fedora container images in older releases #1546
Description
Some of our tests shared with FCOS build containers locally. Once we branch f-c-c for RHCOS, those container references are never updated. Once those Fedora releases go EOL, their content move. And while it should keep working, hiccups do happen in that transition (see e.g. https://pagure.io/fedora-infrastructure/issue/11221 and https://pagure.io/releng/issue/12204).
But anyway, it's also not great to be relying on EOL content in our tests.
My proposal is to modify those tests to use UBI images on RHCOS, c9s images on SCOS, and Fedora images on FCOS.