Automatic merge from submit-queue (batch tested with PRs 67661, 67497, 66523, 67622, 67632). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Allow headless svc without ports to have endpoints
As cited in
https://github.com/kubernetes/dns/issues/174 - this is documented to
work, and I don't see why it shouldn't work. We allowed the definition
of headless services without ports, but apparently nobody tested it very
well.
Manually tested clusterIP services with no ports - validation error.
Manually tested services with negative ports - validation error.
New tests failed, output inspected and verified. Now pass.
xref https://github.com/kubernetes/dns/issues/174
**Release note**:
```release-note
Headless Services with no ports defined will now create Endpoints correctly, and appear in DNS.
```
1c01372524