TestAuthInfo class in test_v3_auth made more efficient.

The TestAuthInfo class inheriting from class RestfulTestCase
is ineffcient because it causes backend databases and
fixtures to be loaded unnecessarily.

Moved auth building helper functions from RestfulTestCase to a new
class AuthTestMixin

Change-Id: If5c187e4f2a5871fd9ad41d90de4d5ddecd75153
Closes-Bug: #1134836
Consolidate provider calls to token_api.create_token

Ensure that token_api.create_token is only called from a single
location within the token provider common logic. This allows for
the token_provider calls to create_token to be overridden looking
towards a scenario where a provider will not actually store the
token data (ephemeral tokens).

Change-Id: Ia091ccfa4638f7307588f7c0c443b28126ee6359
bp: non-persistent-tokens
Merge "TestAuthInfo class in test_v3_auth made more efficient."
Merge "Consolidate provider calls to token_api.create_token"