Description of problem: When using ClusterUDN with localnet topology the traffic don't egress to the external world.

Version-Release number of selected component (if applicable): 4.19

How reproducible: Always

Steps to Reproduce:

1. Create ClusterUDN as follows:

apiVersion: k8s.ovn.org/v1
kind: ClusterUserDefinedNetwork
metadata:
  name: br0-network
spec:
  namespaceSelector:
    matchLabels:
      env: dev
  network:
    topology: Localnet
    localnet:
      role: Secondary
      physicalNetworkName: br0-network
      ipam: {lifecycle: Persistent}
      subnets: ["192.169.0.0/16" ] 

2.     Create a Pod in the target namespace and try ping 8.8.8.8

Actual results: We should be able to send the traffic out as per the doc https://docs.redhat.com/en/documentation/openshift_container_platform/4.19/html-single/multiple_networks/index#nw-cudn-localnet_about-user-defined-networks