Added the ClientThreadsRespecter sync primitive.

This it not to avoid the delay.

This is to ensure that the 2nd client that is created within this test does not outlive the instance of ```ClientThreadsRespecter```.

Without this object in scope, the ```ClientThreadsRespecter``` object may get deleted before another client is attempted to be created off it. And I would like to have this test also cover the logic of not being able to spawn another client after the destruction process has been initiated.