controller.py: clear pending packets on disconnect.

cxn.py: store switch addr to detect when switch has disconnected and
reconnected.
diff --git a/src/python/oftest/controller.py b/src/python/oftest/controller.py
index b4c3ac5..3b2dc43 100644
--- a/src/python/oftest/controller.py
+++ b/src/python/oftest/controller.py
@@ -444,6 +444,8 @@
             self.switch_socket.close()
             self.switch_socket = None
             self.switch_addr = None
+            with self.packets_cv:
+                self.packets = []
             with self.connect_cv:
                 self.connect_cv.notifyAll()