Graceful shutdown of runner container doesn't work

Issue Summary

When we execute docker stop -t 120 <runner-container-name>, it doesn't shut down gracefully.

When stopping a container, Docker will send SIGTERM immediately and SIGKILL if the container is still running after a delay. The argument for -t specifies how many seconds to wait between the two signals.

SIGTERM tells the runner to shut down cleanly. Ideally, the runner should finish what it's currently doing and then shut down without requesting more work.

Steps to Reproduce

execute the following command on the runner hosts machine terminal, when no pipeline build is getting executed on the self-hosted runner

docker stop -t 60 <runner-container-name>

Expected Results

• If the runner is idle it stops immediately
• If the runner is busy it completes the current test pipeline and then stops
• If the runner has not become idle after 60 seconds it stops unconditionally

Actual Results

• The runner does not shut down immediately if it is idle.
• The runner does not stop next time it becomes idle.
• After exactly 60 seconds the runner shuts down causing whatever test it's running at that time to fail.

Workaround

• Perform a manual stop on the container verifying that there are no builds running on the pipelines UI
• With the use of Pipelines APIs, verify if there is a pipeline running on a particular repository and verify the status of the pipelines build and script to stop the runner container using `docker stop` command