make run_tests.sh run devstack unit tests

run_tests.sh was created as an entry point for bashate. We stopped
using it now that we know how to run bashate directly in the gate.
We lost running an unrelated bashate test when that happened.

Devstack does have unit tests. We don't run them. We should.
Especially when working on things like the LIBS_FROM_GIT which is
sufficiently tricky that we really need to add unit tests to ensure
that we don't break it.

Conflicts:
	run_tests.sh

Change-Id: Ife067855569e2eae4c085471d326e8086de37332
(cherry picked from commit 9f20ea13826234ac2c508ea1d50a0822b68d42dc)
support installing clients and supporting libraries at released versions

expand the devstack support for libraries from released versions to
support python-* clients and supporting libraries. This is a collapse
of the master patch series that took a while to get correct.

add unit tests for GIT* definitions

This adds unit tests for all the GIT* definitions, ensuring that for
libraries we think should be defined, they are. It exposed a bug in
glance_store definitions in the process.

The GITDIR definition for python-openstackclient is moved to stackrc
for testability.

Change-Id: I26fac0ccf8fd4818e24618d56bf04b32306f88f6
Merge branch 'stable/juno' into staging/junoplus