filebrowswer: add removeclass for drag and drop hover

vispa/extensions/file/static/js/base/events.js

@@ -200,6 +200,7 @@ var FileBaseEvents = Class.extend({
 
     node.on('drop', function(event) {
       event.preventDefault();
+      $(node).removeClass("file-dragover");
       fileToBeMoved = (event.originalEvent.dataTransfer.getData('dataName'));
       if (fileToBeMoved == "") {
         if (data.type == "d") {