Add Diskmode nonpersistent for batch attachment

[skogta]

What this PR does / why we need it:
Add DiskMode nonpersistent as VM operator is also going to allow it for traditional VMs being imported into K8s.

Testing done:
Ran make images.

WCP precheckin: https://jenkins-vcf-csifvt.devops.broadcom.net/job/wcp-instapp-e2e-pre-checkin/482/
VKS precheckin: https://jenkins-vcf-csifvt.devops.broadcom.net/view/instapp/job/vks-instapp-e2e-pre-checkin/483/

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: skogta
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[k8s-ci-robot]

Hi @skogta. 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.

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[deepakkinni]

FAILED --- Jenkins Build #482

[deepakkinni]

FAILED --- Jenkins Build #508