fix 'killall' in setup fixture for open source

looks like `killall` cannot be found in the docker container. Need to verify that and install it if it is missing from the image.

Start with the setup fixture and the Docker image used by the testing framework. Verify whether `killall` is available inside the container, then check that the fixture completes successfully with the required utility present. Done means the image provides `killall` and the setup fixture no longer fails because it cannot find it.

Written by the indexing model from the issue text.