Automatic merge from submit-queue

add cronjobs to all

Categories were added to the discovery API, but the `kubectl` plumbing didn't make it.  We *did* make `kubectl all` gate on discovery information, so it can least be a superset.  

`cronjobs` are user resources, so I've added them to the list.

@kubernetes/sig-cli-misc 

```release-note
added cronjobs.batch to all, so kubectl get all returns them.
```