Remove unused libvirt-service.json file

This file is a duplicate of nova-libvirt-service.yaml and is presumably
a merge accident after all service files were converted to yaml.

Change-Id: I89719e084fcea7010dd6a29beba999e04989d8c5

k8s/service/libvirt-service.json

-{
-  "id": "libvirt",
-  "kind": "Service",
-  "apiVersion": "v1beta1",
-  "port": 16509,
-  "containerPort": 16509,
-  "selector": {
-    "name": "nova-compute"
-  }
-}