This adds five persistent fixtures for Scenario test cases; previously
they had been variously mocked, patched, etc., in different ways
individually in many test cases. It improves the way those fixtures
are used, mostly by using the .return_value attribute of Mock objects
instead of calling the Mock objects in the test cases and dealing with
strange side effects of that. It also adds assertions for
get_from_manager() calls.
Change-Id: I81a69683ef8ca0fc00bb408c951ec2f9a98e7ba0
434e8173fa