fix: do not error during pytest teardown after test failure

[roypat]

During pytest teardown, we explicitly kill all microvms that a test might have left behind. We do this by reading Firecracker's pid file and then SIGKILL-ing the process. However, if a test fails, we also try to upload its entire jail to S3 as buildkite artifacts, for post-mortem analysis. Here, we are moving instead of copying files, to save on disk space. This is a problem though, as the pid file is inside the jail, and this moving happens before the call to .kill() (and has to happen before, as killing a VM cleans up its jail). This leads to duplicate pytest errors every time a test fails: One for the actual failure, and then a second failure from Microvm.kill() due to the pid file not being found.

Fix this by reverting the commit that changed the copy to a move - we copy outside of the RAM disk, so space is not actually a concern

Changes

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Reason

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License Acceptance

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CONTRIBUTING.md.

PR Checklist

• I have read and understand CONTRIBUTING.md.
• I have run tools/devtool checkstyle to verify that the PR passes the
  automated style checks.
• I have described what is done in these changes, why they are needed, and
  how they are solving the problem in a clear and encompassing way.
• I have updated any relevant documentation (both in code and in the docs)
  in the PR.
• I have mentioned all user-facing changes in CHANGELOG.md.
• If a specific issue led to this PR, this PR closes the issue.
• When making API changes, I have followed the
  Runbook for Firecracker API changes.
• I have tested all new and changed functionalities in unit tests and/or
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• I have linked an issue to every new TODO.

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• This functionality cannot be added in rust-vmm.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.93%. Comparing base (bb2d000) to head (441ed6f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5184      +/-   ##
==========================================
+ Coverage   82.88%   82.93%   +0.05%     
==========================================
  Files         250      250              
  Lines       26936    26936              
==========================================
+ Hits        22325    22339      +14     
+ Misses       4611     4597      -14     

Flag	Coverage Δ
5.10-c5n.metal	83.37% <ø> (ø)
5.10-m5n.metal	83.37% <ø> (ø)
5.10-m6a.metal	82.58% <ø> (-0.01%)	⬇️
5.10-m6g.metal	79.19% <ø> (ø)
5.10-m6i.metal	83.36% <ø> (-0.01%)	⬇️
5.10-m7a.metal-48xl	82.57% <ø> (?)
5.10-m7g.metal	79.19% <ø> (ø)
5.10-m7i.metal-24xl	83.32% <ø> (?)
5.10-m7i.metal-48xl	83.32% <ø> (?)
5.10-m8g.metal-24xl	79.19% <ø> (?)
5.10-m8g.metal-48xl	79.19% <ø> (?)
6.1-c5n.metal	83.42% <ø> (+<0.01%)	⬆️
6.1-m5n.metal	83.41% <ø> (ø)
6.1-m6a.metal	82.63% <ø> (ø)
6.1-m6g.metal	79.19% <ø> (ø)
6.1-m6i.metal	83.41% <ø> (+<0.01%)	⬆️
6.1-m7a.metal-48xl	82.62% <ø> (?)
6.1-m7g.metal	79.19% <ø> (ø)
6.1-m7i.metal-24xl	83.43% <ø> (?)
6.1-m7i.metal-48xl	83.42% <ø> (?)
6.1-m8g.metal-24xl	79.19% <ø> (?)
6.1-m8g.metal-48xl	79.19% <ø> (?)

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