use iptables as default proxy mode

roles/kubernetes/node/defaults/main.yml

@@ -29,7 +29,7 @@ kube_log_dir: "/var/log/kubernetes"
 
 dns_domain: "{{ cluster_name }}"
 
-kube_proxy_mode: userspace
+kube_proxy_mode: iptables
 
 # An experimental dev/test only dynamic volumes provisioner,
 # for PetSets. Works for kube>=v1.3 only.