set a few things in ansible.cfg
set a few things in ansible.cfg

this change sets the following in ansible.cfg because these things
drive me batty:

- gathering = smart

  only gather facts once per host per playbook run, rather than for
  every play.

- command_warnings = False

  yes, we *know* we're using curl instead of get_url.

- retry_files_enabled = False

  prevent ansible droppings

Change-Id: Icd8cc389102599a05313ccf3c244825452d85662

redhat-openstack/tripleo-quickstart,redhat-openstack/tripleo-quickstart