Ignore unresolved dependencies

Commands affecting containers in isolation should not fail because of missing/cyclic dependencies when attempting to ordering them if explicit order is missing. Typical use-case is to pipe the output of `crane status` limited to a certain group (that might have unresolved dependencies) in a script.
You're rIght, I shouldn't have touched that line at all. So I am assuming you meant "still apply when `reversed` is false"? I will update this, but I can't come up with a way to write a test for it, as the `container.running()` and `container.exists()` can't be mocked currently (and revisiting the design to make the `docker`-centric functions mockable/stubbable would need a separate PR).