Set expiration time for `run_cleanup` task.
    
    This prevents situation when all backends are broken for long time
    (hours/days) and queue of run_cleanup tasks grow up and once
    backends come online, they are flooded with run_cleanup tasks.
    
    Also use `schedule_compose` in views.py.
    
    Signed-off-by: Jan Kaluza <jkaluza@redhat.com>