v2 volume: always set unmapMarkSnapChainRemoved to disabled

[derekbit]

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Which issue(s) this PR fixes:

Issue https://github.com/longhorn/longhorn/issues/7534

What this PR does / why we need it:

The field is not meaningful for v2 volumes.

Special notes for your reviewer:

Additional documentation or context

[shuo-wu]

For v2 volumes, it seems that we cannot do snapshot auto deletion together with unmap without modifying spdk_tgt. Is asking users to set up a snapshot deletion recurring job an alternative?

[derekbit]

For v2 volumes, it seems that we cannot do snapshot auto deletion together with unmap without modifying spdk_tgt. Is asking users to set up a snapshot deletion recurring job an alternative?

Yes, the alternative solution sounds feasible. snapshot auto deletion together with unmap -> I think we can improve it in the future if users request the feature. WDYT?

[shuo-wu]

I think we can improve it in the future if users request the feature. WDYT?

This feature is for Longhorn only. Should we modify spdk code for it? I think the alternative solution is good enough.

[derekbit]

I think we can improve it in the future if users request the feature. WDYT? This feature is for Longhorn only. Should we modify spdk code for it?

No.

I think the alternative solution is good enough.

I agree that the alternative solution is enough.

[mergify[bot]]

This pull request is now in conflict. Could you fix it @derekbit? 🙏

[derekbit]

Reviewd in https://github.com/longhorn/longhorn-manager/pull/2642/commits