fix: controller-manager panic when kubeconfig set filed insecure-skip-tls-verify

[xyz-li]

What this PR does / why we need it: Fix controller-manager panic when kubeconfig set filed insecure-skip-tls-verify to true.

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 #1504

Special notes for your reviewer:

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[irfanurrehman]

@xyz-li thanks for doing this. /lgtm

[hectorj2f]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hectorj2f, xyz-li

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