Actually close the atomic feedback context

The `close()` method was called, but I forgot to actually turn off atomic
feedback mode!

Fixes #41.

src/main/java/edu/umich/soar/visualsoar/mainframe/feedback/FeedbackManager.java

@@ -37,6 +37,7 @@ public void close() {
                 + FeedbackManager.this.getClass().getName()
                 + " had already exited atomic feedback mode");
       }
+      inAtomicFeedback = false;
     }
   }