Use the right variable name for switch_name

Change-Id: I761f62cfc2b08ba348c76137a3f658121b115739
diff --git a/util.py b/util.py
index b9ed137..3c68040 100644
--- a/util.py
+++ b/util.py
@@ -25,7 +25,7 @@
             s.switch_connect(config.switches[switch_name].username,
                              config.switches[switch_name].password,
                              config.switches[switch_name].enable_password)
-            ret[switch] = 'Found switch %s with %d ports' % (switch, len(s.switch_get_port_names()))
+            ret[switch_name] = 'Found switch %s with %d ports' % (switch_name, len(s.switch_get_port_names()))
             s.switch_disconnect()
             del(s)