Only run apt-get update if a ppa has changed

gistfile1.txt

Run apt-get update on ppa additions:
  module.wait:
    - name: pkg.refresh_db

Ensure openstack ppa:
  pkgrepo.managed:
    - ppa: openstack-ubuntu-testing/juno
    - refresh_db: False
    - watch_in:
      - module: pkg.refresh_db

Ensure salt ppa:
  pkgrepo.managed:
    - ppa: saltstack/salt
    - refresh_db: False
    - watch_in:
      - module: pkg.refresh_db