Convert control loop tests over to simulated event loop

This makes it so that we properly only use ShmEventLoop for running in
realtime on a robot.  Very nice.

Change-Id: I46b770b336f59e08cfaf28511b3bd5689f72fff1
diff --git a/frc971/wpilib/loop_output_handler.h b/frc971/wpilib/loop_output_handler.h
index 3c95408..81baa68 100644
--- a/frc971/wpilib/loop_output_handler.h
+++ b/frc971/wpilib/loop_output_handler.h
@@ -19,8 +19,7 @@
 // long efficiently.
 //
 // The intended use is to have a subclass for each loop which implements the
-// pure virtual methods and is then run in a separate thread. The operator()
-// loops writing values until Quit() is called.
+// pure virtual methods.
 template <typename T>
 class LoopOutputHandler {
  public:
@@ -44,8 +43,6 @@
     });
   }
 
-  void Quit() { event_loop_->Exit(); }
-
   // Note, all subclasses should call Stop.
   virtual ~LoopOutputHandler() {}