switch hardlink id from int64 to bytes

weed/util/bytes.go

@@ -143,8 +143,8 @@ func RandomInt32() int32 {
 	return int32(BytesToUint32(buf))
 }
 
-func RandomInt64() int64 {
-	buf := make([]byte, 8)
+func RandomBytes(byteCount int) []byte {
+	buf := make([]byte, byteCount)
 	rand.Read(buf)
-	return int64(BytesToUint64(buf))
+	return buf
 }