This makes several improvements to the unit tests for the Authenticate
scenario:
* Unit tests were in two files; one test was duplicated. They are
combined into a single file that is the same predictable place as
the other scenario unit tests.
* Mocking of the Scenario.clients function is made consistent with the
other scenario unit tests.
* Other misc. cleanup.
Change-Id: Iaa86ef514534ada00e868be564f0b6acd6b11ff1
895ce942c3