Description of problem:
Per this comment:
https://issues.redhat.com/browse/OCPBUGS-513?focusedCommentId=20845901&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-20845901

We need to add a note about that when the LowNodeUtilization strategy is enabled for the descheduler, the kube-system and openshift-* namespace exclusion is not applicable.

Users must set the priority class of these protected namespaces to system critical as a workaround, to guarantee exclusion from eviction.

Set to either system-node-critical or system-cluster-critical:

system-node-critical      2000001000   false            72m
system-cluster-critical   2000000000   false            72m