Introduce new option to list test cases.
And return a dummy mac on get_mac failure
diff --git a/src/test/utils/OnosFlowCtrl.py b/src/test/utils/OnosFlowCtrl.py
index 323a720..0aed3d1 100644
--- a/src/test/utils/OnosFlowCtrl.py
+++ b/src/test/utils/OnosFlowCtrl.py
@@ -8,7 +8,10 @@
 
 def get_mac(iface = 'ovsbr0', pad = 4):
     s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
-    info = fcntl.ioctl(s.fileno(), 0x8927, struct.pack('256s', iface[:15]))
+    try:
+        info = fcntl.ioctl(s.fileno(), 0x8927, struct.pack('256s', iface[:15]))
+    except:
+        info = ['0'] * 24
     return '0'*pad + ''.join(['%02x' %ord(char) for char in info[18:24]])
 
 class OnosFlowCtrl: