rpmbuild: make sure librepo/libdnf is always up2date
    
    Librepo/libdnf is clearly part of the dnf/rpm family, so if we
    expect that builders have the latest packaging stack -- we should
    take care of those two (new) packages as well.
    
    This commit is triggered by the need to update librepo/libdnf from
    the bodhi update [1], which should solve major problems with
    downloading mirrorlists, metalinks but individual RPMs as well.
    For more info see [2, 3].
    
    [1] https://bodhi.fedoraproject.org/updates/FEDORA-2019-13479b151a
    [2] https://pagure.io/fedora-infrastructure/issue/7987
    [3] https://github.com/rpm-software-management/librepo/pull/159