Route's k8s Service External Name is self-referential

Since we switched to `svc.cluster.local` as the default domain in https://github.com/knative/serving/pull/13259

There's a short window, between creating the Route's K8s Servcie and the KIngress being reconciled, where we create K8s services with an ExternalName that points to itself.

This causes a bunch of warnings in the kube-system.

ie. we create
```yaml
apiVersion: v1
kind: Service
metadata:
annotations:
labels:
serving.knative.dev/route: some-service
serving.knative.dev/service: some-service
name: some-service
namespace: some-namespace
spec:
externalName: some-service.some-namespace.svc.cluster.local
ports:
- name: http2
port: 80
protocol: TCP
targetPort: 80
sessionAffinity: None
type: ExternalName
status:
loadBalancer: {}
```

Not sure what the right thing to do here - but it was a red herring when the `net-*` plugin couldn't reconcile resources. In theory maybe a headless service would work here but then we're consuming a cluster ip for no reason.

Start by tracing the Route Kubernetes Service creation and KIngress reconciliation described in the issue, using the switch to svc.cluster.local and the net-* plugin reconciliation window as entry points. Reproduce the self-referential ExternalName warning and determine the intended Service behavior; done means the temporary Service configuration no longer points to itself and the kube-system warnings are avoided.

Written by the indexing model from the issue text.