Add NAD as shortName for NetworkAttachmentDefinition

[yossisegev]

Currently NetworkAttachmentDefinition has only "net-attach-def" as a short-name. This doesn't really make life easier, as we use this CRD kind quite a lotin CLI ("oc get network-attachment-definition", etc.).
Can you please add "nad" as a short-name?
Thanks.

[ormergi]

I agree, nad is way more convenient then net-attach-def, hope it will be accepted 🙏