Automatic merge from submit-queue

API v1: do not require ports for all types of services

Ports values had to be specified for all types of services but object with service type "ExternalName" does't define ports. That's why we had to remove required condition.
Presence of ports in service types where ports are actually required is verified here: 
https://github.com/kubernetes/kubernetes/blob/master/pkg/api/validation/validation.go#L2439

For more information about ExternalName services see:
http://kubernetes.io/docs/user-guide/services/#services-without-selectors

Fixes https://github.com/kubernetes/kubernetes/issues/34394