[Task]: Determine if signal killed process

[michael-duren]

What needs to be done

Currently in container.go's Kill method when a signal is sent to the contaniers PID we assume it is killed and update state to specs.StateStopped.
Previously efforts to determine if the process was killed used kill -s 0 or unix.Kill(c.State.Pid, 0) which don't handle zombie processes. This causes the state to not be updated correctly when the process dies later on.

Acceptance criteria

• A new method to determine process status OR logic is updated to determine if the signal actually kills the process.
• Update test cases in container_test.go to test for this.

Parent / tracking issue (optional)

No response

Blocked by (optional)

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Implementation notes (optional)

No response

Rough size (optional)

S — a few hours