Revert to using OVS default OpenFlow versions.

It makes sense to follow Open vSwitch's lead here.
OVS 2.3 enables OpenFlow 1.0 through 1.3 by default.
OVS 2.0 has incomplete support for 1.3, but you can enable
it with protocols=OpenFlow13

mininet/node.py

@@ -1054,14 +1054,14 @@ class OVSSwitch( Switch ):
     "Open vSwitch switch. Depends on ovs-vsctl."
 
     def __init__( self, name, failMode='secure', datapath='kernel',
-                  inband=False, protocols='OpenFlow10,OpenFlow13', **params ):
+                  inband=False, protocols=None, **params ):
         """Init.
            name: name for switch
            failMode: controller loss behavior (secure|open)
            datapath: userspace or kernel mode (kernel|user)
            inband: use in-band control (False)
-           protocols: use specific OpenFlow version(s)
-           Unspecified (or old OVS version) uses default (OpenFlow 1.0)"""
+           protocols: use specific OpenFlow version(s) (e.g. OpenFlow13)
+           Unspecified (or old OVS version) uses OVS default"""
         Switch.__init__( self, name, **params )
         self.failMode = failMode
         self.datapath = datapath