When the TC merged I2637dd714cbb6d38ef8b8dc1083e359207118284 we're
supposed to invoke stestr rather than testr so lets do that
Change-Id: I9e92cfb7419afb281a021645b4b58f29b89c90a8
Properly sets up the mistral-extra repository with packaging and testing
setup, in order to add gating in CI.
Change-Id: I204745785e63cc8b1ae47da5cc59eda6da18b722
Depends-On: I5e75914e500837babdeb358a76ec7d90c56f61ac