Fix some threaded RTS bugs:

 - in awaitRequests(), it was possible to return immediately even
   though wait was set to rtsTrue.  This lead to a busy wait loop,
   so I've disabled that case (see code for details).

 - using PulseEvent in abandonRequestWait() wasn't the right thing,
   because it exposed a race condition.  Again, see the comment in
   the code for details.