Session Manager in 15.2.69 stops working sometimes

[Alexandre Machado]

I reviewed the clean up thread code and I couldn't find anything that could break it (unless something really unexpected happens, e.g. a CoInitialize() call fails...) but there are some points for improvement.

I'm adding some more protection and logging to the clean up thread execution code, in such a way that, unless the memory is corrupted and the execution code is really fubared, it should be more resilient to unexpected factors (and the logging should make it more clear about those issues).