Incorrect return code

[CThuleHansen]

FmuContainer.cpp can only return true or false. However, in some cases FATAL occurs (e.g. https://github.com/INTO-CPS-Association/fmu-rabbitmq/blob/development/rabbitmq-fmu/src/FmuContainer.cpp#L723) but it is swallowed by

fmu-rabbitmq/rabbitmq-fmu/src/fmu.cpp

Lines 490 to 494 in 886f657

	if (fmu != nullptr && fmu->step(currentCommunicationPoint, communicationStepSize)) {
	return fmi2OK;
	}
	return fmi2Discard;

and reduced to a fmi2Discard, which is wrong.

[gitting-around]

we need to check the fmi standard on what should be returned there.