When we added rabbitmq usage within Tornado, we inadvertently caused
the Tornado ioloop to be initialized in runtornado.py's imports,
before we overwrote the _poll method. The end result was that we
weren't running the our instrumented Tornado poll function.
Fix this by moving that code to its own file which we import at the
top of runtornado.py, and adding comments documenting the situation so
we don't break this in some future import reorganization.
(imported from commit 016717476f10566fef4ed2b656f29f865d2084db)
Tim Abbott