verify no advice use happens during shutdown

[ichthyo]

The way the AdviceSystem is implemented (currently, 6/10) introduces several loopholes, races and possible access to already deleted objects, in case any access happens during the final, dtor-invoking phase of the application shutdown. As our general policy is to disallow any significant operations to go on after the end of main(), just ignoring these problems seems a reasonable tradeoff.

This ticket is to remind us later to verify this assessment.