openshift.io/scc: restricted-readonly when setting up router sharding

When setting up router sharding with `endpointPublishingStrategy: Private` in a OCP 4.13.11 BareMetal cluster, the restricted-readonly scc is added to the router pods. Causing them to CrashLoopBackOff:

~~~
$ oc get pod -n openshift-ingress router-spinque-xxx -oyaml | grep -i scc
openshift.io/scc: restricted-readonly <<<
$ oc get pod -n openshift-ingress router-spinque-xxxj -oyaml | grep -i scc
openshift.io/scc: restricted-readonly <<<<
$ oc get pod -n openshift-ingress router-spinque-xxx -oyaml | grep -i scc
openshift.io/scc: restricted-readonly <<<<
~~~
~~~
router-spinque-xxx 0/1 CrashLoopBackOff 27 2h
router-spinque-xxx 0/1 CrashLoopBackOff 27 2h
router-spinque-xxx 0/1 CrashLoopBackOff 27 2h
~~~

Please find the must-gather as well as the sos-report from one of the nodes in the case 03624389 in supportshell

—

The following scc config can be used to reproduce this issue on any platform:

allowPrivilegeEscalation: true
allowedCapabilities: []
apiVersion: security.openshift.io/v1
defaultAddCapabilities: null
fsGroup:
  type: MustRunAs
groups:
- system:authenticated
kind: SecurityContextConstraints
metadata:
  name: bad-router
priority: 0
readOnlyRootFilesystem: true
requiredDropCapabilities:
- KILL
- MKNOD
- SETUID
- SETGID
runAsUser:
  type: MustRunAsRange
seLinuxContext:
  type: MustRunAs
supplementalGroups:
  type: RunAsAny
users: []
volumes:
- configMap
- downwardAPI
- emptyDir
- persistentVolumeClaim
- projected
- secret

Save the above yaml as bad-router-scc.yaml then apply it to your cluster:

$ oc apply -f bad-router-scc.yaml

Force the restart of router pods, such as by deleting one:

$ oc delete pod router-default-6465854689-gvjhs

The newly started pod(s) should be running but not ready, with the bad-router scc:

$ oc get pods
NAME                              READY   STATUS    RESTARTS   AGE
router-default-6465854689-7x558   0/1     Running   0          49s
$ oc get pod router-default-6465854689-7x558 -o yaml|grep scc
    openshift.io/scc: bad-router

If you wait long enough, it will restart multiple times, and eventually enter the CrashLoopBackOff state