Add response header timeouts (#9170)

- Add conservative timeouts upto 3 minutes
  for internode communication
- Add aggressive timeouts of 30 seconds
  for gateway communication

Fixes #9105
Fixes #8732
Fixes #8881
Fixes #8376
Fixes #9028

cmd/gateway/gcs/gateway-gcs.go

@@ -1,5 +1,5 @@
 /*
- * MinIO Cloud Storage, (C) 2017, 2018 MinIO, Inc.
+ * MinIO Cloud Storage, (C) 2017-2020 MinIO, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -184,7 +184,7 @@ func (g *GCS) NewGatewayLayer(creds auth.Credentials) (minio.ObjectLayer, error)
 	metrics := minio.NewMetrics()
 
 	t := &minio.MetricsTransport{
-		Transport: minio.NewCustomHTTPTransport(),
+		Transport: minio.NewGatewayHTTPTransport(),
 		Metrics:   metrics,
 	}