Add distro/release inferring from koji_tag
    
    The same idea of inferring distro/release as in D778 just applied to koji_tag.
    This will make sure that all our current tests actually run on the "best" available image.
    At the moment, upgradepath/depcheck run on "default fallback", which proved to be counter-intuitive
    
    Differential Revision: https://phab.qadevel.cloud.fedoraproject.org/D838