Mark the service as readonly in the UI in authpam plugin
    
    Update the Option class to take a readonly keyword argument,
    defaulting to False. Extend its subclasses to pass this value
    along.
    
    The page template will add the disabled keyword to input and
    textarea if a config option is marked as readonly.
    
    https://fedorahosted.org/ipsilon/ticket/6
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>