Use a constant for the default playlist file name

MediaBrowser.LocalMetadata/Savers/PlaylistXmlSaver.cs

@@ -11,6 +11,9 @@ namespace MediaBrowser.LocalMetadata.Savers
 {
     public class PlaylistXmlSaver : BaseXmlSaver
     {
+        public const string DefaultPlaylistFilename = "playlist.xml";
+
+
         public override bool IsEnabledFor(BaseItem item, ItemUpdateType updateType)
         {
             if (!item.SupportsLocalMetadata)
@@ -45,7 +48,7 @@ namespace MediaBrowser.LocalMetadata.Savers
                 return Path.ChangeExtension(itemPath, ".xml");
             }
 
-            return Path.Combine(path, "playlist.xml");
+            return Path.Combine(path, DefaultPlaylistFilename);
         }
 
         public PlaylistXmlSaver(IFileSystem fileSystem, IServerConfigurationManager configurationManager, ILibraryManager libraryManager, IUserManager userManager, IUserDataManager userDataManager, ILogger logger)