Signed-off-by: John Howard <jhoward@microsoft.com>
This is a follow-on from https://github.com/moby/moby/pull/38277
but had to be done in a couple of stages to ensure that CI didn't
break. v1.1 of the busybox image is now based on a CMD of "sh"
rather than using an entrypoint. And it also uses the bin directory
rather than `c:\busybox`. This makes it look a lot closer to the
Linux busybox image, and means that a couple of Windows-isms in
CI tests can be reverted back to be identical to their Linux
equivalents.
