fix compilation error on 386

Update github.com/safchain/ethtool to fix the compilation
error on 386. Also added 386 to the tarvis yaml.

Fixes #322

Signed-off-by: Moshe Levi <moshele@mellanox.com>

vendor/github.com/safchain/ethtool/README.md

@@ -33,6 +33,7 @@ func main() {
 	if err != nil {
 		panic(err.Error())
 	}
+	defer ethHandle.Close()
 
 	// Retrieve tx from eth0
 	stats, err := ethHandle.Stats("eth0")