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

- Set ['openstack']['block-storage']['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: I2e88e8ff7d5fa8f5d0d611e916eff65ddff8e85e
Addresses: blueprint uniform-region
Merge "Utilise ['openstack']['region'] from cookbook-openstack-common"