AuthorizationSessionTestFixture inherits from ServiceContextMongodTest. The ServiceContextMongodTest constructor runs first and launches a separate thread for the JournalFlusher. The AuthorizationSessionTestFixture::setup() implementation runs after that and resets the AuthorizationManager to a separate instance. This can cause race conditions which result in transient failures.

We should avoid resetting AuthorizationManager altogether in AuthorizationSessionTestFixture. If we have to, then we should ensure that the JournalFlusher is not started until the authorization manager has been fully reset.