[t:4368], fix bug

git-svn-id: file:///svn/toku/tokudb@38604 c7de825b-a66e-492c-adef-691d508d4ae1

newbrt/brt-hot-flusher.c

@@ -285,6 +285,7 @@ toku_brt_hot_optimize(BRT brt,
             // Since there are no children to flush, we should abort
             // the HOT call.
             flusher.rightmost_leaf_seen = 1;
+            toku_unpin_brtnode_off_client_thread(brt->h, root);
         }
 
         // Set the highest pivot key seen here, since the parent may