Fix repos definitions for kiwibuild cloud and container build tasks
    
    The repos attribute is supposed to be a list of URLs, which are comma-
    separated. The missing comma meant that this would not work as intended.
    Furthermore, the cloud image composes were not correctly set up so that
    released updates would be consumed, so that is now fixed.
    
    Signed-off-by: Neal Gompa <ngompa@fedoraproject.org>