Clarified some log messages for negotiating OpenFlow versions. More...

Clarified some log messages for negotiating OpenFlow versions. More importantly, included a patch to ignore all PORT_STATUS messages during the WaitFeaturesReplyState. OVS will periodically send such a message if it's connecting to the controller and being created (e.g. by mininet) at the same time. We will explicitly query the port status/configuration later, so ignoring this message now is fine.