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/tasks/main.yml

@@ -1,4 +1,9 @@
 ---
+- set_fact:
+    standalone_kubelet: >-
+      {%- if inventory_hostname in groups['kube-master'] and inventory_hostname not in groups['kube-node'] -%}true{%- else -%}false{%- endif -%}
+  tags: facts
+
 - include: install.yml
   tags: kubelet