Add CEL expression to ignore default/openshift-ovn-kubernetes NAD to prevent circular dependency where ovn-k fails to start because multus webhook blocks NAD creation, while webhook uses cluster-networked pdos which require ovn-k to be running.

Order of events on install:

1. OVN-Kubernetes and Multus manifests(webhook included) get applied.
2. OVN-Kubernetes starts and tries to apply the default NAD but fails because the webhook is not running:

failed to run ovnkube: failed to start cluster manager: failed to ensure default network nad exists: Internal error occurred: failed calling webhook "multus-validating-config.k8s.io": failed to call webhook: Post "https://multus-admission-controller.openshift-multus.svc:443/validate?timeout=30s": no endpoints available for service "multus-admission-controller" 

1. Multus webhook doesn't start because it is a cluster-networked deployment so it depends on ovn-k being up.