testing: e2e ctr tests do not clean up properly in case of failure

[cmainas]

When running e2e tests for ctr, if a test fails, then there is a high chance that the testing code does not remove the container. When this happens, then it is impossible to re-run the same test in the same machine, because there are leftover containers in ctr with the same name.

=== RUN   TestCtr/Firecracker-linux-environment-variables                                      
    tests_skeleton.go:80: Failed to run unikernel container: ctr: snapshot "Firecracker-linux-e
nvironment-variables": already exists -- exit status 1                                         
--- FAIL: TestCtr (61.10s)  

To fix this, when a tr test fails, we need to make sure that the testing code removes the respective container.

[vliaskov]

Hi, I wrote 2 separate solutions/patches, see above, but I am not sure either is the correct approach. I can open a PR later if one is deemed appropriate.

[vliaskov]

Cleanups of containers and snapshots in ctr tests do happen successfully now.

By the way, I get other issues in some tests now, but I think they should be handled in separate bugs e.g.

=== RUN   TestCtr/Firecracker-linux-hello-world
    tests_skeleton.go:80: Failed to run unikernel container: time="2025-10-24T12:59:19+02:00" level=warning msg="Failed to load urunc log/metrics config from /etc/urunc/config.toml: open /etc/urunc/config.toml: no such file or directory. Using default configuration." subsystem=unikontainers
        time="2025-10-24T12:59:19+02:00" level=warning msg="Failed to load urunc log/metrics config from /etc/urunc/config.toml: open /etc/urunc/config.toml: no such file or directory. Using default configuration." subsystem=unikontainers
        no such file or directory -- exit status 1

[gntouts]

Hey @vliaskov , thanks for your time and effort in contributing to urunc! The warnings you see are expected, since urunc attempts to load a non-existing configuration file.
I will check both of your approaches, verify which one is best suited for our case and come back to you.

[gntouts]

Hello @vliaskov and thank you once again.
Based on my testing, issue305-v1 works as expected and seems a bit cleaner to me. I would suggest using this branch for the fix.

Please feel free to submit a PR from issue305-v1 whenever you're ready!