Address standalone kubelet config case

Also place in global vars and do not repeat the kube_*_config_dir
and kube_namespace vars for better code maintainability and UX.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

roles/kubernetes/node/templates/kubelet-container.j2

@@ -3,7 +3,7 @@
 --net=host --pid=host --name=kubelet --restart=on-failure:5 \
 -v /etc/cni:/etc/cni:ro \
 -v /opt/cni:/opt/cni:ro \
--v /etc/kubernetes:/etc/kubernetes \
+-v {{kube_config_dir}}:{{kube_config_dir}} \
 -v /sys:/sys \
 -v /dev:/dev \
 -v {{ docker_daemon_graph }}:/var/lib/docker \