fix(nginx-system): Fix external IP address handling

This patch should fix the external IP address handling to prevent
rewriting of the external IPs by kube-proxy and allow features like
source-whitelisting to work as expected.

References:
https://kubernetes.io/docs/concepts/services-networking/service/#external-traffic-policy
https://kubernetes.github.io/ingress-nginx/deploy/baremetal/#over-a-nodeport-service