Enable selection of kubeproxy mode

Addressed review comments

roles/openshift_node/tasks/main.yml

@@ -33,6 +33,7 @@
       set_node_ip: "{{ openshift_set_node_ip | default(None) }}"
       node_image: "{{ osn_image | default(None) }}"
       ovs_image: "{{ osn_ovs_image | default(None) }}"
+      proxy_mode: "{{ openshift_node_proxy_mode | default('iptables') }}"
 
 # We have to add tuned-profiles in the same transaction otherwise we run into depsolving
 # problems because the rpms don't pin the version properly. This was fixed in 3.1 packaging.

roles/openshift_node/templates/node.yaml.v1.j2

@@ -35,3 +35,6 @@ servingInfo:
   keyFile: server.key
 volumeDirectory: {{ openshift.common.data_dir }}/openshift.local.volumes
 {% include 'partials/kubeletArguments.j2' %}
+proxyArguments:
+  proxy-mode:
+     - {{ openshift.node.proxy_mode }}