add firewall rules for node exporter

playbooks/azure/openshift-cluster/build_node_image.yml

@@ -22,6 +22,7 @@
       openshift_node_bootstrap: True
       skip_node_svc_handlers: True
       openshift_additional_repos: "{{ azure_node_repos[ansible_distribution] }}"
+      openshift_node_open_ports: [{"service":"Node exporter metrics", "port":"9100/tcp"}]
       openshift_node_include_control_plane: True
       openshift_control_plane_static_pod_location: /etc/origin/node/disabled/
       openshift_node_group_cloud_provider: azure