Adds basic support for configuring various parts of the tests to
make it easier to use them in environments which are configured
differently to DevStack. Specifically in this case the motivation
is to run the Monasca Tempest tests in Kolla CI.
This should be a NOOP change for existing environments.
Change-Id: If6be3a4d54a7b10c3ff40f9ed34045c50ffc3bae