using Module apt: only_upgrade is wrong

[richar...@gmail.com]

Hello,

Having either apt: only_upgrade=docker-engine in my playbook or running it on the command line as ansible all --sudo -m apt -a 'only_upgrade=docker-engine' fails with

```

xx.xxx.xx.xxx | FAILED! => {

    "changed": false, 

    "failed": true, 

    "msg": "Boolean docker-engine not in either boolean list"

}

```

In the document

only_upgrade(added in 2.1)

Only install/upgrade a package if it is already installed.

my local ansible version is

```

ansible 2.1.0.0

  config file = /etc/ansible/ansible.cfg

  configured module search path = ['/usr/share/ansible']

```

and my host docker-engine version is 1.11.0,

Using only_upgrade way is wrong?

Thanks!