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.
Oh yes, `false` :). Yea testing that is a bit tricky. I'm actually not quite sure how to mock those out, which is why I haven't done so far. Seems quite cumbersome to do it, at least I haven't found a satisfying solution.