Disable sending FedMsg notifications by default
    
    Pagure does not currently mandate FedMsg integration to be configured
    for initial setup, but if it isn't installed and configured, a lot of
    regular tasks break due to tracebacks from missing or broken FedMsg
    setups.
    
    This was necessary for fixing Pagure on Mageia and openSUSE.
    
    Merges https://pagure.io/pagure/pull-request/3269
    
    Signed-off-by: Neal Gompa <ngompa13@gmail.com>
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>