Qt4: don't "leak" playlist items

There was opportunity for playlist items not showing up in Qt playlist due to race between playlist rebuilding and item-added, item-removed callbacks
Maybe also fixes some aspects of #2297 or completely - to test.

modules/gui/qt4/components/playlist/playlist_model.cpp

@@ -89,6 +89,7 @@ PLModel::PLModel( playlist_t *_p_playlist,  /* THEPL */
     ADD_ICON( NODE, ":/type/node" );
 #undef ADD_ICON
 
+    addCallbacks();
     rebuild( p_root, true );
     CONNECT( THEMIM->getIM(), metaChanged( input_item_t *),
             this, processInputItemUpdate( input_item_t *) );
@@ -700,11 +701,6 @@ void PLModel::rebuild()
 void PLModel::rebuild( playlist_item_t *p_root, bool b_first )
 {
     playlist_item_t* p_item;
-    /* Remove callbacks before locking to avoid deadlocks
-       The first time the callbacks are not present so
-       don't try to delete them */
-    if( !b_first )
-        delCallbacks();
 
     /* Invalidate cache */
     i_cached_id = i_cached_input_id = -1;
@@ -730,8 +726,6 @@ void PLModel::rebuild( playlist_item_t *p_root, bool b_first )
     reset();
 
     emit currentChanged( index( currentItem, 0 ) );
-
-    addCallbacks();
 }
 
 void PLModel::takeItem( PLItem *item )