[IPv6] backend pool name should be case-insensitive

[lzhecheng]

What type of PR is this?

/kind bug

What this PR does / why we need it:

[IPv6] backend pool name should be case-insensitive

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

[IPv6] backend pool name should be case-insensitive

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

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lzhecheng

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[MartinForReal]

/lgtm

[lzhecheng]

/retest

[MartinForReal]

/retest

[lzhecheng]

/cherrypick release-1.27

[k8s-infra-cherrypick-robot]

@lzhecheng: once the present PR merges, I will cherry-pick it on top of release-1.27 in a new PR and assign it to you.

In response to this:

/cherrypick release-1.27

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-infra-cherrypick-robot]

@lzhecheng: new pull request created: #3938

In response to this:

/cherrypick release-1.27

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.