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.
```
1dbe09b1f6