Adds Cinder client

This change adds Cinder client in services/volume

* Keeps existing tests for Compute Extensions in tempest/tests/compute
* Copies existing volumes test to tests/volume and refactors them to test the
Cinder API, and adds a BaseVolumesTest class
* Renames the Nova Extensions' volumes_client to volumes_extensions_client
* Adds build_interval and build_timeout parameters in config for Cinder
specific tests
* Renames build_interval and build_timeout environment variables in the
Devstack template file to COMPUTE_BUILD_INTERVAL and COMPUTE_BUILD_TIMEOUT
* Adds volume specific environment variables VOLUME_BUILD_INTERVAL AND
VOLUME_BUILD_TIMEOUT to the Devstack template file.

Fixes LP Bug #1026190

Change-Id: I14d980ada1ddb29e8147f990aaf239fdcaae5eb6
18 files changed