Fix issue #538 Long scan times from additional HTTP requests

- For embedded photos it only checked the current index file for duplicates.
- Now all index files and archives are checked, if enabled.

src/TumblThree/TumblThree.Applications/Downloader/AbstractDownloader.cs

@@ -527,6 +527,10 @@ protected void OnSaveTimedEvent(IProgress<Exception> progress)
         public virtual bool CheckIfPostedUrlIsDownloaded(string url)
         {
             var filenameUrl = url.Split('/').Last();
+            if (shellService.Settings.LoadAllDatabases)
+            {
+                return managerService.CheckIfFileExistsInDB(filenameUrl, true, shellService.Settings.LoadArchive);
+            }
             return files.CheckIfFileExistsInDB(filenameUrl, true);
         }