Observed this issue on Ubuntu 14. The test named in the subject hangs because the LauncherDecorator in WithContainerStep is not able to kill the Docker container processes it started (via docker exec). The ps command it executes (looking for the COOKIE env variable on the process) is not finding the processes. It's as though the processes are not inheriting the env variables.
If ps is the problem, we could use /proc directly, but it is probably an actual problem of the environment variables.
Also we should do a hard kill on the container after 10+ seconds.