Remove the return instruction when the state is not final
In the generation of code, in the file activity.c, there is a return instruction after the call of the thread's main function. This is not correct when the thread is not actived in all modes, because it ends the thread whereas it should just iterate on the loop.
The origin of this line is in the file AadlBaToCUnparser.java at the line 649 in the project fr.tpt.aadl.ramses.generation.c.