fixed error

implementation/mininet_controller.py

@@ -662,6 +662,7 @@ def run(topology, test=None, limit=None, delay=None, shortcut=False):
 
 
 if __name__ == '__main__':
+    global packet_counter_initialized
     setLogLevel('info')
     parser = argparse.ArgumentParser()
     parser.add_argument('--tests', help='list all available tests for a topology', action='store_true')
@@ -706,6 +707,7 @@ if __name__ == '__main__':
         run(args.topo, args.test, bw_limit, delay, use_shortcut)
         sleep(1)
         use_shortcut = True
+        packet_counter_initialized = False
         run(args.topo, args.test, bw_limit, delay, use_shortcut)
     else:
         run(args.topo, args.test, bw_limit, delay, use_shortcut)