bump minimal ansible version to 2.8.0 (#5984)

* bump minimal ansible version to 2.8.0

* check ansible version in separate playbook

remove-node.yml

@@ -1,17 +1,6 @@
 ---
-- hosts: localhost
-  become: no
-  gather_facts: no
-  tasks:
-    - name: "Check ansible version >=2.7.8"
-      assert:
-        msg: "Ansible must be v2.7.8 or higher"
-        that:
-          - ansible_version.string is version("2.7.8", ">=")
-      tags:
-        - check
-  vars:
-    ansible_connection: local
+- name: Check ansible version
+  import_playbook: ansible_version.yml
 
 - hosts: "{{ node | default('etcd:k8s-cluster:calico-rr') }}"
   gather_facts: no