Fix bug when run queues get decommissioned before poll thread

The atexit handler that cleans up the run queues can run before the
atexit handler that tells the poll thread to shutdown.  This is
inherently racy.  But until I come up with a proper long-term fix,
this commit makes the race harder to trigger.
Don't check the ops pointer, now that we switch it

After cc4bd019b2b72aa, these asserts can legitimately fail.