Backport of CSL-13047: fix for segmentation fault or SIGSEGV with consul-cni network plugin's code on 1.9.1 into release/1.7.x

[vdinesh4738]

This PR is copy auto-generated from #5062 to be assessed for backporting due to the inclusion of the label backport/1.7.x.

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The below text is copied from the body of the original PR.

Provided fix for the segmentation fault or SIGSEGV with consul-cni network plugin's code, which is common across the platform till date on Multus cni extension.

Background:
As per jira, when we enable cni and Multus, and then deploy the application with the api-resource 'network-attachment-definition' annotation like 'k8s.v1.cni.cncf.io/networks': '[{"namespace": "consul", "name":"consul-consul-cni"}]' is attached to the application pod, the application pod fails to come up at pod init with error in

Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create pod network sandbox. (more detailed in the jira: https://hashicorp.atlassian.net/browse/CSL-13047

Root cause:
Creation of client with unavailable Kubeconfig or with the wrong Kubeconfig file name causing nil pointer dereference.

Fix:
Created the function to looks/fetch the latest Kubeconfig file and creates client.

Validation:
With the cni and Multus enabled: we update the iptables in the pod network ns.
With this fix : App is up and running and the iptables are updated in the pod network ns.

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