Add a ContainerClient and container API tests

This change adds a ContainerClient for testing the
Barbican container API. It adds a container test suite
and integrates the ContainerClient with the plugin
testing infrastructure.

Change-Id: I930455c6ae1e1127706480f24c0ea46f5cc81e85
Depends-On: I27f15375c46faa48cd56c8d52ecfd585fb325239
Implements: bp tempest-plugin
5 files changed