🐛 Skip checking clusterConfiguration.dns fields when KCP checking MachineNeedRollout

[Levi080513]

What this PR does / why we need it:

KCP uses the following method to update the coredns version, this does not require rolling updates of control plane nodes, and we can optimize it.

cluster-api/controlplane/kubeadm/internal/controllers/controller.go

Lines 466 to 469 in 9d36ddc

	// Update CoreDNS deployment.
	if err := workloadCluster.UpdateCoreDNS(ctx, controlPlane.KCP, parsedVersion); err != nil {
	return ctrl.Result{}, errors.Wrap(err, "failed to update CoreDNS deployment")
	}

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes # #9832

Test:

1. Create CAPI Cluster with dns config.

kc get kcp -n default hw-sks-test-no-gpu-controlplane -ojson | jq '.spec.kubeadmConfigSpec.clusterConfiguration.dns'
{
  "imageRepository": "registry.smtx.io/kubesmart/coredns",
  "imageTag": "v1.10.1"
}

2. Then update the dns config.

kc get kcp -n default hw-sks-test-no-gpu-controlplane -ojson | jq '.spec.kubeadmConfigSpec.clusterConfiguration.dns'

{
  "imageRepository": "registry.smtx.io/kubesmart/coredns",
  "imageTag": "v1.11.0"
}

3. KCP is ready and CP Machine no need rolling update.

kc get kcp -n default hw-sks-test-no-gpu-controlplane
NAME                              CLUSTER              INITIALIZED   API SERVER AVAILABLE   REPLICAS   READY   UPDATED   UNAVAILABLE   AGE   VERSION
hw-sks-test-no-gpu-controlplane   hw-sks-test-no-gpu   true          true                   3          3       3         0             17h   v1.25.15

kc get machine -n default -l cluster.x-k8s.io/cluster-name=hw-sks-test-no-gpu,cluster.x-k8s.io/control-plane=
NAME                                    CLUSTER              NODENAME                                PROVIDERID                                   PHASE     AGE   VERSION
hw-sks-test-no-gpu-controlplane-2gmhm   hw-sks-test-no-gpu   hw-sks-test-no-gpu-controlplane-nw86c   elf://d29afee9-03ab-440c-a294-64afd5b67adf   Running   17h   v1.25.15
hw-sks-test-no-gpu-controlplane-f4x7n   hw-sks-test-no-gpu   hw-sks-test-no-gpu-controlplane-h2k4j   elf://c663ea39-865d-473b-8a30-56b4dc22a032   Running   17h   v1.25.15
hw-sks-test-no-gpu-controlplane-mzph8   hw-sks-test-no-gpu   hw-sks-test-no-gpu-controlplane-pztmt   elf://0f0ef45c-7b95-4b68-8a58-06b9235a1ae7   Running   17h   v1.25.15

4. Workload cluster DNS config has been updated.

kc get deploy coredns -n kube-system -ojson | jq '.spec.template.spec.containers[].image'
"registry.smtx.io/kubesmart/coredns/coredns:v1.11.0"

kc get cm kubeadm-config -n kube-system -oyaml | yq '.data.ClusterConfiguration'  | yq '.dns'
imageRepository: registry.smtx.io/kubesmart/coredns
imageTag: v1.11.0

/area provider/control-plane-kubeadm

[k8s-ci-robot]

Hi @Levi080513. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[g-gaston]

looks good, thanks for the change!

[g-gaston]

/ok-to-test
/lgtm

thanks for this fix!

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 19458370dc6e3198ed88ac98d1e3d9345f95cdb6

[sbueringer]

Thx!

/assign @fabriziopandini

[fabriziopandini]

Nice change!
Sorry for taking a little bit longer than usual to get to this
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fabriziopandini

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[fabriziopandini]

/hold
for squash

[sbueringer]

Enabled squash :)

/hold cancel

[Levi080513]

@sbueringer
Sorry to bother you, can this PR be picked up to the release-1.5 ? We still use CAPI 1.5 internally, but this improvement is needed for us.

[sbueringer]

/cherry-pick release-1.6

[sbueringer]

/cherry-pick release-1.5

[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #10303

In response to this:

/cherry-pick release-1.6

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #10304

In response to this:

/cherry-pick release-1.5

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.