smart incubator crashs and service does not restart

[qgeissmann]

This happens upon, mysql exception ...

[qgeissmann]

@ggilestro in 365019c, I stop and join the serial/DB thread in a try/finally block. It is possible that the thread was not closed before in case of exception, which lead to inability to resume...
We did more refactoring with @nazabic. but have not merged yet (this patch cold make master more stable until then). Let me know if any issue arises/if the problem persists.