Do not use ‘yes/no’ for boolean values (#11472)

Consistent boolean values in ansible playbooks

roles/adduser/vars/coreos.yml

@@ -3,6 +3,6 @@ addusers:
   - name: kube
     comment: "Kubernetes user"
     shell: /sbin/nologin
-    system: yes
+    system: true
     group: "{{ kube_cert_group }}"
-    create_home: no
+    create_home: false