CentOS Stream 9 is close to be released, and official mirrors are
already poplated. This patch is adding support to centos-minimal in CS9.
Also enable centos-minimal/[8,9]-stream-build-succeeds tests.
This patch is being tested together with [1] to apply following list of elements:
vm centos-minimal simple-init growroot nodepool-base openstack-repos infra-package-needs
[1] https://review.opendev.org/c/openstack/project-config/+/811442
Change-Id: Iecf7f7e4c992bb23437b6461cdd04cdca96aafa6
