[release-4.17] NO-ISSUE: Fix unittest for CleanupBackups

[openshift-cherrypick-robot]

This is an automated cherry-pick of #638

/assign donpenney

/cherrypick release-4.16 release-4.15 release-4.14

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: donpenney

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/openshift-kni/lifecycle-agent/blob/release-4.17/OWNERS)~~ [donpenney] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[openshift-cherrypick-robot]

@openshift-cherrypick-robot: new pull request created: #647

In response to [this](): >This is an automated cherry-pick of #638 > >/assign donpenney > >/cherrypick release-4.16 release-4.15 release-4.14 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.