can not create podgroup for single pod without ownerreference

[sivanzcw]

/kind bug

What happened:
can not create podgroup for single pod without ownerreference
What you expected to happen:
single pod can be scheduled successufully

create single pod

kubectl create -f myapp-deploy.yaml

apiVersion: v1
kind: Pod
metadata:
  name: myapp-deploy
  namespace: default
spec:
  containers:
  - image: ikubernetes/myapp:v1
    imagePullPolicy: IfNotPresent
    name: myapp-containers
    ports:
    - containerPort: 80
      name: http
      protocol: TCP
    resources:
      requests:
        cpu: "1"
  dnsPolicy: ClusterFirst
  schedulerName: volcano
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300

view logs of volcano-controllers

kubectl logs volcano-controllers-57864457d4-shfkv -n volcano-system | grep myapp-deploy

E1029 13:03:54.365619       1 pg_controller.go:136] Failed to handle Pod <default/myapp-deploy>: PodGroup.scheduling.sigs.dev "podgroup-817afc91-fa4c-11e9-b688-fa163ec79500" is invalid: [metadata.ownerReferences.kind: Invalid value: "": kind must not be empty, metadata.ownerReferences.name: Invalid value: "": name must not be empty]
E1029 13:04:14.857172       1 pg_controller_handler.go:94] Failed to create normal PodGroup for Pod <default/myapp-deploy>: PodGroup.scheduling.sigs.dev "podgroup-817afc91-fa4c-11e9-b688-fa163ec79500" is invalid: [metadata.ownerReferences.kind: Invalid value: "": kind must not be empty, metadata.ownerReferences.name: Invalid value: "": name must not be empty]
E1029 13:04:14.857214       1 pg_controller.go:136] Failed to handle Pod <default/myapp-deploy>: PodGroup.scheduling.sigs.dev "podgroup-817afc91-fa4c-11e9-b688-fa163ec79500" is invalid: [metadata.ownerReferences.kind: Invalid value: "": kind must not be empty, metadata.ownerReferences.name: Invalid value: "": name must not be empty]

podgroup creating failed for wrong configuraiton of kind and name of ownerreference

[hzxuzhonghu]

For the pod not controlled by any resource, let's set the PG ownerref as the pod itself.

[sivanzcw]

#499