Treat NoRouteToHostException as a failed fetch

[gianm]

It's possible to get NoRouteToHostExceptions as well as ConnectExceptions when attempting to connect to the kafka broker. I don't think any others are possible, at least based on the docs at http://docs.oracle.com/javase/6/docs/api/java/net/SocketException.html (BindException and PortUnreachableException shouldn't be possible for TCP connects).