Revert "Preparser: yield the playlist (NSDRCID 1)"

This reverts commit f3b97438.

It creates a circular reference holding. (playlist is the parent of the preparser and hold a reference to the preparser during all the preparser life's span).

src/playlist/engine.c

@@ -479,7 +479,7 @@ void playlist_LastLoop( playlist_t *p_playlist )
  */
 void playlist_PreparseLoop( playlist_preparse_t *p_obj )
 {
-    playlist_t *p_playlist = pl_Yield( p_obj );
+    playlist_t *p_playlist = (playlist_t *)p_obj->p_parent;
     input_item_t *p_current;
     int i_activity;
 
@@ -557,7 +557,6 @@ void playlist_PreparseLoop( playlist_preparse_t *p_obj )
         vlc_object_lock( p_obj );
     }
     vlc_object_unlock( p_obj );
-    pl_Release( p_obj );
 }
 
 /**