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/disk/stat_windows.go

@@ -19,9 +19,10 @@
 package disk
 
 import (
-	"os"
 	"syscall"
 	"unsafe"
+
+	os2 "github.com/minio/minio/pkg/x/os"
 )
 
 var (
@@ -43,7 +44,7 @@ var (
 // https://msdn.microsoft.com/en-us/library/windows/desktop/aa364937(v=vs.85).aspx
 func GetInfo(path string) (info Info, err error) {
 	// Stat to know if the path exists.
-	if _, err = os.Stat(path); err != nil {
+	if _, err = os2.Stat(path); err != nil {
 		return Info{}, err
 	}