Our tests are only for the compute API (and related compute things).
They are not scenario tests as defined in the Tempest scenario README.
This patch moves our tests to subclass the Tempest base compute test
class. While this isn't guaranteed to be a stable interface, it's
convenient enough (we gain helper methods) that the potential
maintenance overhead is deemed worth it. Our unit tests are also moved
up a directory, with tests/ now being only for unit tests and
tempest/api for our test cases.
Change-Id: Ie34aa99765c3fa8a136fa4cb1b11edb3d8c76ba3