windows: Support all REPARSE_POINT attrib files properly. (#4203)

This change adopts the upstream fix in this regard at
https://go-review.googlesource.com/#/c/41834/ for Minio's
purposes.

Go's current os.Stat() lacks support for lot of strange
windows files such as

 - share symlinks on SMB2
 - symlinks on docker nanoserver
 - de-duplicated files on NTFS de-duplicated volume.

This PR attempts to incorporate the change mentioned here

   https://blogs.msdn.microsoft.com/oldnewthing/20100212-00/?p=14963/

The article suggests to use Windows I/O manager to
dereference the symbolic link.

Fixes #4122

pkg/quick/encoding.go

@@ -22,11 +22,11 @@ import (
 	"bytes"
 	"encoding/json"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
 
+	os2 "github.com/minio/minio/pkg/x/os"
 	yaml "gopkg.in/yaml.v2"
 )
 
@@ -122,7 +122,7 @@ func saveFileConfig(filename string, v interface{}) error {
 // decoder format according to the filename extension. If no
 // extension is provided, json will be selected by default.
 func loadFileConfig(filename string, v interface{}) error {
-	if _, err := os.Stat(filename); err != nil {
+	if _, err := os2.Stat(filename); err != nil {
 		return err
 	}
 	fileData, err := ioutil.ReadFile(filename)