Configure Loadbalancer back-end pool only for controlplane machines

[Karthik-K-N]

/kind bug /area provider/ibmcloud

What steps did you take and what happened: [A clear and concise description of what the bug is.]

Creating a IBMPowerVS cluster from cluster-template-powervs-create-infra.yaml template creates a Loadbalancer and configures all the machines of the cluster to its backend pool.

What did you expect to happen:

Only control plane machines should be configured to backendpool as 6443 is APIServer port and only control-plane machines will serve in that port.

Changes needs to be done:

1. Just skip configuring LB backend pool for data plane nodes here.
2. Utility function

   available in capi repo for identifying machine as control-plane machine

Anything else you would like to add: [Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster-api version:
• Minikube/KIND version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[Karthik-K-N]

/good-first-issue

[k8s-ci-robot]

@Karthik-K-N: This request has been marked as suitable for new contributors.

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In response to [this](https://github.com/kubernetes-sigs/cluster-api-provider-ibmcloud/issues/1990): >/good-first-issue Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes-sigs/prow](https://github.com/kubernetes-sigs/prow/issues/new?title=Prow%20issue:) repository.

[carmal891]

/assign