Add `runSleepingContainer` and `runSleepingContainerInImage` helper
functions to factor out the way to run system-specific idle containers.
Define a sleeping container as command `top` in image `busybox` for
Unix and as command `sleep 60` in image `busybox` for Windows. Provide a
single point of code to update those.
Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>
Upstream-commit: 777ee34b075292e5aee16c4088444508899f8f35
Component: engine
7f9cdda847