webui: replace action_buttons with action_widget
    
    Simplify code base by reuse of 'disable' feature of button_widget. All
    occurrences of action-button which were disabled/enabled were replaced
    by button-widget.
    
    https://fedorahosted.org/freeipa/ticket/4258
    
    Reviewed-By: Endi Sukma Dewata <edewata@redhat.com>