thread state coordinator: add test to be explicit about resume behavior in...

thread state coordinator: add test to be explicit about resume behavior in presence of deferred stop notification still pending.

There is a state transition that seems potentially buggy that I am capturing and
logging here, and including an explicit test to demonstrate expected behavior.  See new test
for detailed description.  Added logging around this area since, if we hit it, we
may have a usage bug, or a new state transition we really need to investigate.

This is around this scenario:
Thread C deferred stop notification awaiting thread A and thread B to stop.
Thread A stops.
Thread A requests resume.
Thread B stops.

Here we will explicitly signal the deferred stop notification after thread B
stops even though thread A is now resumed.  Copious logging happens here.

llvm-svn: 218683