use released library versions by default

This patch provides a new path for installing libraries in devstack so
that it's possible to either test with upstream released libraries, or
with git versions of individual libraries.

Libraries are added by name to 3 associative arrays GITREPO,
GITBRANCH, GITDIR. When we get to the library install phase we inspect
LIBS_FROM_GIT and look for libraries by name (i.e. "oslo.config") and
if they exist we'll clone and install those libraries from
git. Otherwise we won't, and just let pip pull them as dependencies
when it needs them.

This patch provides the conversion of the oslo libraries, including
pbr.

Devstack-gate jobs for these libraries will need to change to support
actually forward testing their content.

restructure stackrc into groupings

in order to support installing from stable libraries we first need to
actually sort out all the categories our giant list of git repos fit
into. This will make it much easier to not lose one in the process.

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.

(This is a collapsed patchset for backport to make backport fixups easier)

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.

Conflicts:
	lib/glance

Change-Id: I26fac0ccf8fd4818e24618d56bf04b32306f88f6
Source functions from stackrc

stackrc now requires GITREPO, GITBRANCH, GITDIR and has been
dependent on functions for a while (is_package_installed).  Ensure
we source the required functions file when stackrc is loaded.  Avoids
unexpected issues in grenade where they may or may not have been loaded
depending on the configuration.

Closes-bug: #1377274

Change-Id: I5027cfad07af0de7ff39f424601d6f7ec5dcadae
(cherry picked from commit 0e4cd038287bcf36ff31c4e7b22266051198b44c)
Merge branch 'stable/icehouse' of https://github.com/openstack-dev/devstack into stable/icehouse

Conflicts:
	stackrc