only recreate the lazy when needed

MediaBrowser.Controller/BaseItemManager/BaseItemManager.cs

@@ -107,9 +107,12 @@ namespace MediaBrowser.Controller.BaseItemManager
         /// Creates the metadata refresh throttler.
         /// </summary>
         private void SetupMetadataThrottler()
+        {
+            if (MetadataRefreshThrottler == null || MetadataRefreshThrottler.IsValueCreated)
             {
                 MetadataRefreshThrottler = new Lazy<SemaphoreSlim>(() => new SemaphoreSlim(_metadataRefreshConcurrency));
             }
+        }
 
         /// <summary>
         /// Returns the metadata refresh concurrency.