[cinder-csi-plugin] Fix volume from snapshot AZ selection

[carterpewpew]

What this PR does / why we need it:

When restoring a volume from a snapshot in a multi-AZ cluster with volumeBindingMode: WaitForFirstConsumer, the topology-derived availability zone can conflict with the snapshot's AZ. Cinder requires the new volume to be in the same AZ as the snapshot, so it rejects the request with HTTP 400: "Volume must be in the same availability zone as the snapshot". This happens because the scheduler picks a node (and therefore an AZ) before the CSI driver gets called, and that AZ gets passed straight to Cinder's volume create without considering what AZ the snapshot lives in. The fix clears the topology derived AZ when creating a volume from a snapshot, letting Cinder auto-select the snapshot's AZ. Explicit availability set via StorageClass parameters is not affected.

Which issue this PR fixes(if applicable):
fixes #3088

Special notes for reviewers:

Only the topology-derived AZ path is changed. If the user explicitly sets availability in StorageClass params, that value is passed through unchanged.

Two tests added:

1. TestCreateVolumeFromSnapshotWithTopology - verifies the AZ is cleared when restoring from snapshot with topology
2. TestCreateVolumeFromSnapshotWithExplicitAvailability - verifies explicit availability param is preserved even with snapshot + topology

Release note:

[cinder-csi-plugin] Fix snapshot restore in multi-AZ clusters with topology-aware provisioning by clearing the topology-derived availability zone and letting Cinder select the snapshot's zone.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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

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

Details

Needs approval from an approver in each of these files:

• 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 @carterpewpew. Thanks for your PR.

I'm waiting for a kubernetes 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.

I understand the commands that are listed here.

Details

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-sigs/prow repository.