[transport] make dial error logging compatible with ECS (#227)

The LoggingDiler was logging an error with the field 'network' set as
the network type (tcp/upd), however 'network' is an object in ECS,
this would cause the log entry to be rejected by Elasticsearch.

transport/logging.go

@@ -33,7 +33,7 @@ type loggingConn struct {
 
 func LoggingDialer(d Dialer, logger *logp.Logger) Dialer {
 	return DialerFunc(func(ctx context.Context, network, addr string) (net.Conn, error) {
-		logger := logger.With("network", network, "address", addr)
+		logger := logger.With("network.transport", network, "server.address", addr)
 		c, err := d.DialContext(ctx, network, addr)
 		if err != nil {
 			logger.Errorf("Error dialing %v", err)