一号坑：-i参数只能定义一次。
开始话题之前，先看一个调用案例：
有playbook如下：
# deploy.yml
- hosts: '{{host_svr}}'
max_fail_percentage: 30
serial: "30%"
remote_user: common
become: true
roles:
- dubbosvr
- hosts: '{{host_web}}'
max_fail_percentage: 30
serial: "30%"
remote_user: common
become: true
roles:
- websvr