Test: Restart ONOS with default network cfg after vrouter/dhcprelay tests are run.
This puts ONOS back to initial state for other tests.

Change-Id: Ib20538399737789c11def76189a77bc651289506
diff --git a/src/test/utils/OnosCtrl.py b/src/test/utils/OnosCtrl.py
index 22afa56..6083d85 100644
--- a/src/test/utils/OnosCtrl.py
+++ b/src/test/utils/OnosCtrl.py
@@ -52,7 +52,7 @@
 
     @classmethod
     def config(cls, config):
-        if config:
+        if config is not None:
             json_data = json.dumps(config)
             resp = requests.post(cls.cfg_url, auth = cls.auth, data = json_data)
             return resp.ok, resp.status_code