Merge pull request #38278 from hodovska/external-name-no-ports

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 kubernetes/kubernetes#34394

apis/openapi-spec/swagger.json

@@ -9774,9 +9774,6 @@
    },
    "v1.ServiceSpec": {
     "description": "ServiceSpec describes the attributes that a user creates on a service.",
-    "required": [
-     "ports"
-    ],
     "properties": {
      "clusterIP": {
       "description": "clusterIP is the IP address of the service and is usually assigned randomly by the master. If an address is specified manually and is not in use by others, it will be allocated to the service; otherwise, creation of the service will fail. This field can not be changed through updates. Valid values are \"None\", empty string (\"\"), or a valid IP address. \"None\" can be specified for headless services when proxying is not required. Only applies to types ClusterIP, NodePort, and LoadBalancer. Ignored if type is ExternalName. More info: http://kubernetes.io/docs/user-guide/services#virtual-ips-and-service-proxies",