Drop hostNetwork from nginx-ingress addon

* Both flannel and Calico support host port via `portmap`
* Allows writing NetworkPolicies that reference ingress pods in `from`
or `to`. HostNetwork pods were difficult to write network policy for
since they could circumvent the CNI network to communicate with pods on
the same node.

addons/nginx-ingress/google-cloud/deployment.yaml

@@ -20,7 +20,6 @@ spec:
     spec:
       nodeSelector:
         node-role.kubernetes.io/node: ""
-      hostNetwork: true
       containers:
         - name: nginx-ingress-controller
           image: quay.io/kubernetes-ingress-controller/nginx-ingress-controller:0.15.0