Make OpenStack related data available in actions

 * Make OpenStack related data accessible via context in action DSL
   without explicitly defining parameters such as auth_token and project_id
 * Make Openstack data accessible via action_context parameter
   for new Actions
 * Unit tests

Implements blueprint: mistral-openstack-data-accessible-by-default

Change-Id: I9b6802d90c0ac17e0494d2025897ce5cdd02f4ee