Update two comments where original API was throwing the wrong HTTP codes

When a container doesn't exist, a 404 should be thrown, not 409 (which is used in other API calls if the container already exists and this is correct)

Also raise a 404 when attempting to delete a container which does not exist (though it's arguable whether a 400 is acceptable too for a delete operation, but I think 404 might be a bit more appropriate)