Prettify and fix yaml indentations

[denzhel]

Having the following example playbooks vars:

    datadog_checks:
      rabbitmq:
        init_config:
        instances:
          - rabbitmq_api_url: 'http://localhost:15672/api/'
            user: 'admin'
            password: 'password'

Will output this default template behavior(ugly and unclean yaml structure):

    init_config: null
    instances:
    -   password: password
        rabbitmq_api_url: http://localhost:15672/api/
        user: admin

Because of:

{{ datadog_checks[item] | to_nice_yaml }}

Adding indent=2 results in a much better and cleaner output:

   init_config: null
   instances:
   - password: password
     rabbitmq_api_url: http://localhost:15672/api/
     user: admin