In the cross project workshop "Establishing key themes for the Mitaka
cycle" [1] during the Mitaka summit, one of the agreed point was to
implement functional tests for the client libraries. [2]
Later on, this will serve to improve our backward compatibility for
client libraries. See I72e4e9cfa0539f6b326a0296c065fa3cb754f8ae
In preparation to implement the functional tests for both v2 and v3
clients, this patch initializes the new directories and adds the base
test classes: V3ClientTestCase and V2ClientTestCase.
Each class instantiates its specific keystoneclient version via
os-client-config either based on a clouds.yaml config file or from the
environment variables.
[1] https://mitakadesignsummit.sched.org/event/edd78ade4c7c92581a7cabc26019a85a
[2] https://etherpad.openstack.org/p/mitaka-crossproject-themes
Change-Id: Ia73d72d5f87051fb46d733782275b548874a1def
f5bcd87e23