The keystoneclient-devstack-functional job works fine when being run
against this repo, but fails when running against the keystone repo
because of conflicts within the tools/test-setup.sh script there.
Do our own definition of the job to make sure that we always run tox
against the correct repo. Also base the job on devstack-minimal to avoid
installing more serviced than needed.
Change-Id: Ie4c03de48a3b7f2fb3967a185486c6fb0d6e0a5f
7d765bf21c