Cleanup and fixes (#3273)

* newRequestID() (previously generateUploadID()) returns string than byte array.
* Remove unclear comments and added appropriate comments.
* SHA-256, MD5 Hash functions return Hex/Base64 encoded string than byte array.
* Remove duplicate MD5 hasher functions.
* Rename listObjectsValidateArgs() into validateListObjectsArgs()
* Remove repeated auth check code in all bucket request handlers.
* Remove abbreviated names in bucket-metadata
* Avoid nested if in bucketPolicyMatchStatement()
* Use ioutil.ReadFile() instead of os.Open() and ioutil.ReadAll()
* Set crossDomainXML as constant.

cmd/api-headers_test.go

@@ -20,9 +20,9 @@ import (
 	"testing"
 )
 
-func TestGenerateRequestID(t *testing.T) {
+func TestNewRequestID(t *testing.T) {
 	// Ensure that it returns an alphanumeric result of length 16.
-	var id = generateRequestID()
+	var id = newRequestID()
 
 	if len(id) != 16 {
 		t.Fail()