* test for openstack inventory constructed functionality
this adds unit tests for the compose, groups, and keyed_var features
of the openstack inventory plugin
* fix constructed functionality in openstack inventory plugin
The compose, groups, and keyed_groups functionality of the openstack
inventory plugin was broken:
- the plugin was not passing the correct variables to the
Constructable methods for compose and groups
- the plugin was simply never calling the appropriate method for
implementing keyed_groups
This commit fixes both issues.
