wrap etag value with double quotes

go/storage/crc.go

@@ -25,5 +25,5 @@ func (c CRC) Value() uint32 {
 func (n *Needle) Etag() string {
 	bits := make([]byte, 4)
 	util.Uint32toBytes(bits, uint32(n.Checksum))
-	return fmt.Sprintf("%x", bits)
+	return fmt.Sprintf("\"%x\"", bits)
 }

go/weed/weed_server/volume_server_handlers.go

@@ -95,7 +95,7 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 		w.WriteHeader(http.StatusNotModified)
 		return
 	}
-	w.Header().Set("Etag", "\""+etag+"\"")
+	w.Header().Set("Etag", etag)
 	if n.NameSize > 0 && filename == "" {
 		filename = string(n.Name)
 		dotIndex := strings.LastIndex(filename, ".")