rmi: resolves image id and removes that

[dweomer]

The way image removal works can lead to an unexpected result in that kim rmi your/image:tag removes all tags that may exist for the underlying image id. This may be a flaw in the CRI implementation.

We should probably re-implement image rm/rmi to work as an "un-tag" operation unless it is the last tag for the image id. This is how docker image rm appears to work.