[occm] Add node affinity to schedule cloud controller manager only on control plane nodes.

[fakman0]

What this PR does / why we need it:
This PR improves the OpenStack Cloud Controller Manager (OCCM) scheduling configuration by replacing the nodeSelector with more flexible nodeAffinity. The change:

• Replaces nodeSelector: node-role.kubernetes.io/control-plane: "true" with nodeAffinity using operator: Exists
• Provides better compatibility across different Kubernetes distributions where control-plane nodes might have the label with different values (empty string "", "true", "yes", etc.)

Which issue this PR fixes(if applicable):
Not related.

Special notes for reviewers:

• The nodeAffinity with operator: Exists only checks for the presence of the node-role.kubernetes.io/control-plane label, regardless of its value
• This approach is more compatible with various Kubernetes distributions (kubeadm, RKE2, k3s, minikube, etc.) that might set different values for the control-plane label
• The scheduling behavior remains the same - OCCM will still only run on control-plane nodes
• nodeAffinity is the recommended modern approach over nodeSelector for more complex scheduling requirements

Release note:

[occm] Improved OCCM scheduling robustness by replacing nodeSelector with nodeAffinity for better compatibility across Kubernetes distributions.

[linux-foundation-easycla]

• ✅login: fakman0 / (468d240)

The committers listed above are authorized under a signed CLA.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign stephenfin for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @fakman0. Thanks for your PR.

I'm waiting for a kubernetes 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

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-sigs/prow repository.

[kayrus]

/ok-to-test

[kayrus]

/test openstack-cloud-controller-manager-ovn-e2e-test
/test openstack-cloud-controller-manager-e2e-test

[bnallapeta]

Can we please merge this once it goes through the due review process? Users have been facing this issue trying to follow out of the box instructions.

cc @kayrus

[fakman0]

@kayrus @mdbooth

[mnaser]

/lgtm

[k8s-ci-robot]

@mnaser: changing LGTM is restricted to collaborators

In response to this:

/lgtm

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-sigs/prow repository.