Add UTCNow() function. (#3931)

This patch adds UTCNow() function which returns current UTC time.

This is equivalent of UTCNow() == time.Now().UTC()

cmd/auth-rpc-client.go

@@ -1,5 +1,5 @@
 /*
- * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ * Minio Cloud Storage, (C) 2016, 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.
@@ -93,7 +93,7 @@ func (authClient *AuthRPCClient) Login() (err error) {
 		Username:    authClient.config.accessKey,
 		Password:    authClient.config.secretKey,
 		Version:     Version,
-		RequestTime: time.Now().UTC(),
+		RequestTime: UTCNow(),
 	}
 
 	reply := LoginRPCReply{}