Update hcsshim tag to v0.10.0-rc.4

Signed-off-by: Kirtana Ashok <Kirtana.Ashok@microsoft.com>

vendor/github.com/Microsoft/hcsshim/internal/wclayer/legacy.go

@@ -8,7 +8,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -377,7 +376,7 @@ func newLegacyLayerWriter(root string, parentRoots []string, destRoot string) (w
 		}
 		w.parentRoots = append(w.parentRoots, f)
 	}
-	w.bufWriter = bufio.NewWriterSize(ioutil.Discard, 65536)
+	w.bufWriter = bufio.NewWriterSize(io.Discard, 65536)
 	return
 }
 
@@ -420,7 +419,7 @@ func (w *legacyLayerWriter) reset() error {
 	if err != nil {
 		return err
 	}
-	w.bufWriter.Reset(ioutil.Discard)
+	w.bufWriter.Reset(io.Discard)
 	if w.currentIsDir {
 		r := w.currentFile
 		br := winio.NewBackupStreamReader(r)
@@ -696,7 +695,7 @@ func (w *legacyLayerWriter) Add(name string, fileInfo *winio.FileBasicInfo) erro
 		// The file attributes are written before the stream.
 		err = binary.Write(w.bufWriter, binary.LittleEndian, uint32(fileInfo.FileAttributes))
 		if err != nil {
-			w.bufWriter.Reset(ioutil.Discard)
+			w.bufWriter.Reset(io.Discard)
 			return err
 		}
 	}