Description of problem:
When the NAD is deleted. The sriov operator did not sync the sriovnetwork to NAD

Version-Release number of selected component (if applicable):
quay.io/openshift-release-dev/ocp-v4.0-art-dev:v4.2.0-201909081401-ose-sriov-network-operator

How reproducible:
alwasy

Steps to Reproduce:
1. Install sriov operator 
2. Create the sriovnetwork CR
 
 apiVersion: sriovnetwork.openshift.io/v1
kind: SriovNetwork
metadata:
  creationTimestamp: "2019-08-27T09:30:26Z"
  generation: 3
  name: example-sriovnetwork
  namespace: sriov-network-operator
  resourceVersion: "9958438"
  selfLink: /apis/sriovnetwork.openshift.io/v1/namespaces/sriov-network-operator/sriovnetworks/example-sriovnetwork
  uid: 4d610e2c-c8ad-11e9-9801-3cfdfeba0aa4
spec:
  ipam: |
    {
      "type": "host-local",
      "subnet": "10.56.217.0/24",
      "rangeStart": "10.56.217.172",
      "rangeEnd": "10.56.217.181",
      "routes": [{
        "dst": "0.0.0.0/0"
      }],
      "gateway": "10.56.217.1"
    }
  networkNamespace: z1
  resourceName: intelnics1
  spoofChk: true
  trust: false
  vlan: 1

3. Check the NAD will be created by sriovoperator

oc get network-attachment-definitions.k8s.cni.cncf.io example-sriovnetwork -n z1
NAME                   AGE
example-sriovnetwork   26m

4. Delete the NAD 
 oc delete network-attachment-definitions.k8s.cni.cncf.io example-sriovnetwork -n z1

5. Check the NAD again
6. Check the sriov operator logs

Actual results:

5. wait a while. Check the NAD do not be created
6. Did not see any sync logs for NAD

Expected results:
The deleted NAD should be restored by sriov operator

Additional info: