test: Improve signal test coverage

[Constantin1489]

#2036 (comment)

also weird thing, I dont see the output from sigshutdown_handler() when running pytest, so pytest might be shutting it down in a weird way

[Constantin1489]

What kind of reason did fail my PR (https://github.com/dgtlmoon/changedetection.io/actions/runs/7257771185/job/19772065566)? it's literally just checking the docker log after the container is shut down but the error comes when the CD is running.
Even my test code didn't run yet and is not related to the test-api. 😂😂

[dgtlmoon]

What kind of reason did fail my PR (https://github.com/dgtlmoon/changedetection.io/actions/runs/7257771185/job/19772065566)? it's literally just checking the docker log after the container is shut down but the error comes when the CD is running. Even my test code didn't run yet and is not related to the test-api. 😂😂

Dont worry about it, it's some random failure due to timing/slowness waiting for response etc

[dgtlmoon]

Current tests pass, can I merge this?