Validate tenant_id part of TempURL in clients

Rackspace Cloud Files uses a UUID for the tenant ID, so move the code that
validates that part of the TempURL to the client.

Change-Id: I996fdc4b4b66e110066353d3b22ea3dab0535a5d
Don't import HeatTestCase directly

Fix the HeatTestCase import issue as required by H302,
a following patch of https://review.openstack.org/#/c/129846/

Change-Id: Iab9a508682e9fe2932b7d00b191c8a4cdea4738b
Merge "Don't import HeatTestCase directly"
Merge "Validate tenant_id part of TempURL in clients"