CentOS Stream 9 has actually been mirrored for years [1] and is currently the only release available. Revert the logic so that DIB_DISTRIBUTION_MIRROR and DIB_EPEL_MIRROR are set when using 9-stream. This should make 9-stream builds finally use CI mirrors and also fix any 10-stream image builds using this element (for example in Kayobe CI). [1] https://review.opendev.org/c/opendev/system-config/+/817900 Change-Id: I1bcb6d972d7d7771257ddc1cb3870fbe3e3db65d Signed-off-by: Pierre Riteau <pierre@stackhpc.com>