Issue #2093 remove ID from the cloned element prior to adding to the DOM.

We should not create a duplicate CSS ID.

Author: vanboom

src/Sortable.js

@@ -924,7 +924,7 @@ Sortable.prototype = /** @lends Sortable.prototype */ {
 		pluginEvent('setupClone', this);
 		if (!Sortable.eventCanceled) {
 			cloneEl = clone(dragEl);
-
+			cloneEl.removeAttribute("id");
 			cloneEl.draggable = false;
 			cloneEl.style['will-change'] = '';