Fix for PONSIM exit issue with execption

Change-Id: Id249cb67760c8aa5708dccca63b60f06608d4900
diff --git a/common/frameio/frameio.py b/common/frameio/frameio.py
index 4ed999e..544d462 100644
--- a/common/frameio/frameio.py
+++ b/common/frameio/frameio.py
@@ -416,3 +416,12 @@
                     break  # break inner loop so we reconstruct sockets list
 
         log.debug('select-loop-exited')
+
+    def del_interface(self, iface_name):
+        """
+            Delete interface for stopping
+        """
+
+        log.info('Delete interface')
+        del self.ports[iface_name]
+        log.info('Interface(port) is deleted')