[release-4.14] OCPBUGS-39238: Fix applying backup label not preserving existing labels

[openshift-cherrypick-robot]

This is an automated cherry-pick of #639

/assign openshift-cherrypick-robot

[openshift-ci-robot]

@openshift-cherrypick-robot: Jira Issue OCPBUGS-39221 has been cloned as Jira Issue OCPBUGS-39238. Will retitle bug to link to clone. /retitle [release-4.14] OCPBUGS-39238: Fix applying backup label not preserving existing labels

In response to [this](https://github.com/openshift-kni/lifecycle-agent/pull/640): >This is an automated cherry-pick of #639 > >/assign openshift-cherrypick-robot Instructions for interacting with me using PR comments are available [here](https://prow.ci.openshift.org/command-help?repo=openshift-kni%2Flifecycle-agent). If you have questions or suggestions related to my behavior, please file an issue against the [openshift-eng/jira-lifecycle-plugin](https://github.com/openshift-eng/jira-lifecycle-plugin/issues/new) repository.

[openshift-ci-robot]

@openshift-cherrypick-robot: This pull request references Jira Issue OCPBUGS-39238, which is invalid:

• release note text must be set and not match the template OR release note type must be set to "Release Note Not Required"
• expected dependent Jira Issue OCPBUGS-39221 to be in one of the following states: VERIFIED, RELEASE PENDING, CLOSED (ERRATA), CLOSED (CURRENT RELEASE), CLOSED (DONE), CLOSED (DONE-ERRATA), but it is MODIFIED instead

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

The bug has been updated to refer to the pull request using the external bug tracker.

In response to [this](https://github.com/openshift-kni/lifecycle-agent/pull/640): >This is an automated cherry-pick of #639 > >/assign openshift-cherrypick-robot Instructions for interacting with me using PR comments are available [here](https://prow.ci.openshift.org/command-help?repo=openshift-kni%2Flifecycle-agent). If you have questions or suggestions related to my behavior, please file an issue against the [openshift-eng/jira-lifecycle-plugin](https://github.com/openshift-eng/jira-lifecycle-plugin/issues/new) repository.

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: donpenney

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

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/openshift-kni/lifecycle-agent/blob/release-4.14/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-ci-robot]

@openshift-cherrypick-robot: Jira Issue OCPBUGS-39238: All pull requests linked via external trackers have merged:

• openshift-kni/lifecycle-agent#640

Jira Issue OCPBUGS-39238 has been moved to the MODIFIED state.

In response to [this](https://github.com/openshift-kni/lifecycle-agent/pull/640): >This is an automated cherry-pick of #639 > >/assign openshift-cherrypick-robot Instructions for interacting with me using PR comments are available [here](https://prow.ci.openshift.org/command-help?repo=openshift-kni%2Flifecycle-agent). If you have questions or suggestions related to my behavior, please file an issue against the [openshift-eng/jira-lifecycle-plugin](https://github.com/openshift-eng/jira-lifecycle-plugin/issues/new) repository.