[SM] State Machine module must not be allowed to stop without exiting the application

Allowing the state machine module to stop without stopping the application poses too many problems and race-conditions.

I decide to remove support for that use case. If a module is started by the framework, it is not allowed to stop prematurely, it can only be stopped during shutdown.

For our application template, that means: If the state machine enters the "exiting" state, it will shut down the complete application.