title: Ansible skip import_playbook with variable definition
body: <p>I have a <code>main.yaml</code> like below:</p>
  <pre>
  - import_playbook: 1.yaml
      
  - import_playbook: 2.yaml
    vars:
      allow2: False 
    when: allow2
  </pre>
  <p>I want the playbook <code>2.yaml</code> can be skipped totally (not try to execute any tasks inside <code>2.yaml</code>).
  But it looks all tasks in <code>2.yaml</code> will be called but not executed.</p>
  <p>File <code>1.yaml</code>:</p>
  <pre>
  - name: Go1
    hosts: test
    gather_facts: false 
  
    tasks:
      - debug: msg="Message from 1.yaml"
  </pre>
  <p>File <code>2.yaml</code>:</p>
  <pre>
  - name: Go2
    hosts: test
    gather_facts: false 
    tasks:
      - debug: msg="Message from 2.yaml"
  </pre>
  <p>The output is:</p>
  <pre>
  $ ansible-playbook main.yaml 
  
  PLAY [Go1] ***********
  TASK [debug] *********
  Thursday 05 October 2017  03:10:12 -0400 (0:00:00.116)       0:00:00.116 ****** 
  ok: [test1] => {}
  
  MSG:
  
  Message from 1.yaml
  
  
  PLAY [Go2] ************
  
  TASK [debug] ************
  Thursday 05 October 2017  03:10:12 -0400 (0:00:00.090)       0:00:00.206 ****** 
  skipping: [test1]
  </pre>
  <p>The you can say the task in <code>2.yaml</code> also was called but skipped.
  But I want no any tasks will be called in <code>2.yaml</code>.</p>
  <p>Is it possible?</p>