Add secure-rbac tests for SecretStores API

This patch adds basic RBAC test for the Secret Stores API for
the reader, member and admin personas with project scope.

The tests are skipped by a config option, as they require
the multiple-backends feature to be enabled in barbican.

The devstack instace we're using for gate tests does not have
this enabled, so we default to False for now.

Change-Id: Ibca9d44fb3d0f4fd9945a7e6c636e0fbf6beb42e
5 files changed