Speed up tasks (#4278)

* fact gathering should run only once per node
* eliminate ansible version check, it is at the beginning of each
  playbook

roles/kubernetes/preinstall/tasks/0020-verify-settings.yml

@@ -1,10 +1,4 @@
 ---
-- name: Stop if ansible version is too low
-  assert:
-    that:
-      - ansible_version.full is version('2.3.0', '>=')
-  run_once: yes
-
 - name: Stop if either kube-master, kube-node or etcd is empty
   assert:
     that: groups.get('{{ item }}')