Update minio-go

vendor/github.com/minio/minio-go/bucket-cache.go

@@ -1,6 +1,6 @@
 /*
  * Minio Go Library for Amazon S3 Compatible Cloud Storage
- * (C) 2015, 2016, 2017 Minio, Inc.
+ * Copyright 2015-2017 Minio, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,7 +18,6 @@
 package minio
 
 import (
-	"encoding/hex"
 	"net/http"
 	"net/url"
 	"path"
@@ -209,11 +208,9 @@ func (c Client) getBucketLocationRequest(bucketName string) (*http.Request, erro
 	}
 
 	// Set sha256 sum for signature calculation only with signature version '4'.
-	var contentSha256 string
+	contentSha256 := emptySHA256Hex
 	if c.secure {
 		contentSha256 = unsignedPayload
-	} else {
-		contentSha256 = hex.EncodeToString(sum256([]byte{}))
 	}
 
 	req.Header.Set("X-Amz-Content-Sha256", contentSha256)