Volume names are validated to be unique and always have been. The cited
issues are all about apply getting messed up, not the aspiserver
allowing dups.
```
$ k create -f /tmp/bad.yaml
The Deployment "bad-volumes-test" is invalid: spec.template.spec.volumes[1].name: Duplicate value: "config"
$ k apply --server-side -f /tmp/bad.yaml
Error from server: failed to create typed patch object (default/bad-volumes-test; apps/v1, Kind=Deployment): .spec.template.spec.volumes: duplicate entries for key [name="config"]
$ k apply -f /tmp/bad.yaml -o json | jq '.spec.template.spec.volumes'
The Deployment "bad-volumes-test" is invalid: spec.template.spec.volumes[1].name: Duplicate value: "config"
```
151509fb74