load vars based on distribution

amazon.yml

# vars/amazon.yml
---
foo: bar

output

TASK: [Group hosts by OS and version] *****************************************
changed: [localhost]

TASK: [debug var=groups] ******************************************************
ok: [localhost] => {
    "groups": {
        "Amazon-2014.03": [
            "localhost"
        ],
        "all": [
            "localhost"
        ],
        "ungrouped": [
            "localhost"
        ]
    }
}

PLAY [Amazon*] ****************************************************************

GATHERING FACTS ***************************************************************
ok: [localhost]
localhost: importing /etc/ansible/vars/amazon.yml

TASK: [do something with vars] ************************************************
changed: [localhost]

TASK: [debug var=foo] *********************************************************
ok: [localhost] => {
    "foo": "bar"
}

PLAY RECAP ********************************************************************
localhost                  : ok=6    changed=2    unreachable=0    failed=0

tmp3.yml

---
- hosts: all
  tasks:
    - name: Group hosts by OS and version
      group_by: key={{ ansible_distribution }}-{{ ansible_distribution_version }}

    - debug: var=groups

- hosts: Amazon*
  vars_files:
    - "vars/{{ ansible_distribution | lower }}.yml"
  tasks:
    - name: do something with vars
      shell: echo {{ foo }}

    - debug: var=foo