Description of problem:

The requirements for hybrid networking has changed and it is no longer supported to start a hybrid network on a running cluster. Currently trying to patch the CNO to enable a hybrid network succeeds and it should fail.  

Version-Release number of selected component (if applicable):
4.5

How reproducible:

Everytime 

Steps to Reproduce:
1. Deploy an openshift cluster with OVNKubernetes 
2. patch the CNO to enable a hybrid network 
3. the patch operation succeeds 

Actual results:
The patch operation is allowed to happen

Expected results:
The patch operation should fail

Additional info:
Patch the CNO so the operator config looks like this 

apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  creationTimestamp: null
  name: cluster
spec:
  clusterNetwork:
  - cidr: 10.128.0.0/14         <- must be the cluster network CIDR
    hostPrefix: 23
  externalIP:
    policy: {}
  networkType: OVNKubernetes
  serviceNetwork:
  - 172.30.0.0/16                <- must be the service network CIDR
  defaultNetwork:
    type: OVNKubernetes
    ovnKubernetesConfig:
      hybridOverlayConfig:
        hybridClusterNetwork:
        - cidr: 10.132.0.0/14    <- must not overlap cluster or service cidr    
          hostPrefix: 23