ipatests: WebUI - ensure that ipa automember-rebuild prints a warning
    
    ipa automember-rebuild now prints a warning about CPU usage
    in the WebUI. Ensure that the warning is properly displayed.
    
    Related: https://pagure.io/freeipa/issue/9320
    
    Signed-off-by: mbhalodi <mbhalodi@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Michal Polovka <mpolovka@redhat.com>