Make ethernet frames 60 bytes for those drivers that actually checks

ethernet frame length.

simulator/ethernet.py

@@ -31,6 +31,8 @@ class ETH(object):
         u = random.uniform(0, 1.0)
         if u >= self.send_loss:
             data = data[0:6] + self.macaddr + data[12:]
+            if len(data) < 60:
+                data = data.ljust(60, '\0')
             self.socket.send(data)
         else:
             logger.log('Dropped sent packet')