move reattaching user data to own function and call it only after fetching metadata for the first time

MediaBrowser.Controller/Persistence/IItemRepository.cs

@@ -35,6 +35,13 @@ public interface IItemRepository
 
     void SaveImages(BaseItem item);
 
+    /// <summary>
+    /// Reattaches the user data to the item.
+    /// </summary>
+    /// <param name="item">The item.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    void ReattachUserData(BaseItem item, CancellationToken cancellationToken);
+
     /// <summary>
     /// Retrieves the item.
     /// </summary>