Draggable: Calling .refreshPositions instead of ._refreshItems when d…

…ragging with a connected sortable to force containerCache initialisation/update. Fixed: #5563 - connectToSortable misbehaves if the position of the sortable changes after the sortable and draggable have been initialised as _refreshItems no longer updating container cache.(cherry picked from commit 84257e7)

ui/jquery.ui.draggable.js

@@ -477,7 +477,7 @@ $.ui.plugin.add("draggable", "connectToSortable", {
 					instance: sortable,
 					shouldRevert: sortable.options.revert
 				});
-				sortable._refreshItems();	//Do a one-time refresh at start to refresh the containerCache
+				sortable.refreshPositions();	// Call the sortable's refreshPositions at drag start to refresh the containerCache since the sortable container cache is used in drag and needs to be up to date (this will ensure it's initialised as well as being kept in step with any changes that might have happened on the page).
 				sortable._trigger("activate", event, uiSortable);
 			}
 		});