Fix the url for the ostree repo
    
    Bodhi updates https://kojipkgs.fedoraproject.org/atomic/25/ on every
    stable update run. We need to point the repo there as the old location
    is what was updated by pungi before F25 release.
    
    Note that https://dl.fedoraproject.org/pub/fedora/linux/atomic/25/
    redirects to https://kojipkgs.fedoraproject.org/atomic/25/.