Fix checking service references from `tags` when deleting PIP

[zarvd]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #7130

Special notes for your reviewer:

Also, this PR deletes some obsolete, unused code.

Does this PR introduce a user-facing change?

Fix checking service references from `tags` when deleting PIP

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: zarvd Once this PR has been reviewed and has the lgtm label, please assign lzhecheng for approval. For more information see the Kubernetes Code Review Process.

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

Needs approval from an approver in each of these files: - **[OWNERS](https://github.com/kubernetes-sigs/cloud-provider-azure/blob/master/OWNERS)** Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[k8s-ci-robot]

Hi @zarvd. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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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.

[MartinForReal]

/ok-to-test

[feiskyer]

Could you fix the unit tests?

[coveralls]

coverage: 76.75% (+0.01%) from 76.737% when pulling 3d9a0c9337ef49798d16984e260774a08f8bb5ae on zarvd:fix/pip/legacy-tag into 93625419e29e443add72aa79cb2377262d614d0b on kubernetes-sigs:master.