Make the path to CS.cfg a class variable
    
    Rather than passing around the path to CS.cfg for the CA and KRA
    set it at object creation and use everywhere.
    
    Make update_cert_config() a real class method instead of a static
    method. It wasn't being called that way in any case and makes it
    possible to use the class config file.
    
    Related: https://pagure.io/freeipa/issue/6703
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Fraser Tweedale <ftweedal@redhat.com>