Utilise ['openstack']['region'] from cookbook-openstack-common

- Set ['openstack']['compute']['region'] to equal ['openstack']['region']
- Add tests for endpoint creation, to confirm region is set.
- Add test to override the endpoint and confirm it is used.

Change-Id: I7f80a049bef0feff85d26ca211d237e208440822
Addresses: blueprint uniform-region
Merge "Utilise ['openstack']['region'] from cookbook-openstack-common"