fix: treat 404 on server delete as success

[nilsherzig]

same as in ServerStateRefreshFunc

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Description

What code changed, and why?

Handling of 404 responses when trying to delete an instance the second time around. Simpler Version of #127, might be easier to merge? Similar logic is already used in the project at:

packer-plugin-openstack/builder/openstack/server.go

Line 45 in a7e79ff

if _, ok := err.(gophercloud.ErrDefault404); ok {

[hashicorp-cla-app]

All committers have signed the CLA.

[Copilot]

Pull request overview

This PR updates the OpenStack builder’s server deletion logic to treat a 404 Not Found response during servers.Delete / servers.ForceDelete as a successful outcome, avoiding failures when cleanup tries to delete the same instance twice (e.g., in volume-based workflows where multiple steps may attempt termination).

Changes:

• Treat gophercloud.ErrDefault404 from server delete operations as success and return nil.
• Emit a user-facing message when the server is already deleted.

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