Adds whoami DS plugin in case that plugin is missing
    
    When first installation of IPA has been done when whoami
    plugin was not enabled in DS by default and then IPA was
    upgraded to newer versions, then after upgrade to IPA 4.5
    WebUI stops working. This is caused by new requirement on
    whoami DS plugin which is used to obtain information about
    logged in entity.
    
    This fix adds the whoami plugin during update in case that the plugin
    is not enabled.
    
    https://pagure.io/freeipa/issue/7126
    
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Tibor Dudlak <tdudlak@redhat.com>