update to safeguard against accidentally passing string instead of list

roles/kubernetes/master/templates/manifests/kube-apiserver.manifest.j2

@@ -81,9 +81,13 @@ spec:
 {% if kube_api_anonymous_auth is defined and kube_version | version_compare('v1.5', '>=')  %}
     - --anonymous-auth={{ kube_api_anonymous_auth }}
 {% endif %}
-{% for flag in apiserver_custom_flags %}
+{% if apiserver_custom_flags is string %}
+    - {{ apiserver_custom_flags }}
+{% else % }
+{%   for flag in apiserver_custom_flags %}
     - {{ flag }}
-{% endfor %}
+{%   endfor %}
+{% endif %}
     livenessProbe:
       httpGet:
         host: 127.0.0.1

roles/kubernetes/master/templates/manifests/kube-controller-manager.manifest.j2

@@ -46,9 +46,13 @@ spec:
     - --configure-cloud-routes=true
     - --cluster-cidr={{ kube_pods_subnet }}
 {% endif %}
-{% for flag in controller_mgr_custom_flags %}
+{% if controller_mgr_custom_flags is string %}
+    - {{ controller_mgr_custom_flags }}
+{% else % }
+{%   for flag in controller_mgr_custom_flags %}
     - {{ flag }}
-{% endfor %}
+{%   endfor %}
+{% endif %}
     livenessProbe:
       httpGet:
         host: 127.0.0.1

roles/kubernetes/master/templates/manifests/kube-scheduler.manifest.j2

@@ -27,9 +27,13 @@ spec:
     - --leader-elect=true
     - --master={{ kube_apiserver_endpoint }}
     - --v={{ kube_log_level }}
-{% for flag in scheduler_custom_flags %}
+{% if scheduler_custom_flags is string %}
+    - {{ scheduler_custom_flags }}
+{% else % }
+{%   for flag in scheduler_custom_flags %}
     - {{ flag }}
-{% endfor %}
+{%   endfor %}
+{% endif %}
     livenessProbe:
       httpGet:
         host: 127.0.0.1