Remove jinja2 dependency of do

While `do` looks cleaner, forcing this extra option in ansible.cfg
seems to be more invasive. It would be better to keep the traditional
approach of `set dummy = ` instead.

ansible.cfg

@@ -13,4 +13,3 @@ callback_whitelist = profile_tasks
 roles_path = roles:$VIRTUAL_ENV/usr/local/share/kubespray/roles:$VIRTUAL_ENV/usr/local/share/ansible/roles:/usr/share/kubespray/roles
 deprecation_warnings=False
 inventory_ignore_extensions = ~, .orig, .bak, .ini, .cfg, .retry, .pyc, .pyo, .creds
-jinja2_extensions = jinja2.ext.do

roles/kubernetes/node/templates/kubelet.standard.env.j2

@@ -83,20 +83,20 @@ KUBELET_HOSTNAME="--hostname-override={{ kube_override_hostname }}"
 {# Kubelet node labels #}
 {% set role_node_labels = [] %}
 {% if inventory_hostname in groups['kube-master'] %}
-{%   do role_node_labels.append('node-role.kubernetes.io/master=true') %}
+{%   set dummy = role_node_labels.append('node-role.kubernetes.io/master=true') %}
 {%   if not standalone_kubelet|bool %}
-{%     do role_node_labels.append('node-role.kubernetes.io/node=true') %}
+{%     set dummy = role_node_labels.append('node-role.kubernetes.io/node=true') %}
 {%   endif %}
 {% else %}
-{%   do role_node_labels.append('node-role.kubernetes.io/node=true') %}
+{%   set dummy = role_node_labels.append('node-role.kubernetes.io/node=true') %}
 {% endif %}
 {% if inventory_hostname in groups['kube-ingress']|default([]) %}
-{%   do role_node_labels.append('node-role.kubernetes.io/ingress=true') %}
+{%   set dummy = role_node_labels.append('node-role.kubernetes.io/ingress=true') %}
 {% endif %}
 {% set inventory_node_labels = [] %}
 {% if node_labels is defined %}
 {% for labelname, labelvalue in node_labels.iteritems() %}
-{% do inventory_node_labels.append(labelname + '=' + labelvalue) %}
+{% set dummy = inventory_node_labels.append(labelname + '=' + labelvalue) %}
 {% endfor %}
 {% endif %}
 {% set all_node_labels = role_node_labels + inventory_node_labels %}