Drop the bz_product_name override
    
    Instead of having a product name and an override via the bz_product_name
    just use always the product name.
    
    This fixes the issue around "Fedora Container Images" which were somehow
    not cached from bugzilla. This led to the script trying to create them
    instead of updating them, which of course failed since they did exist
    in bugzilla.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>