clear tours before registering new tours

src/Umbraco.Web.UI.Client/src/common/services/tour.service.js

@@ -17,6 +17,7 @@
          * Registers all tours from the server and returns a promise
          */
         function registerAllTours() {
+            tours = [];
             return tourResource.getTours().then(function(tourFiles) {
                 angular.forEach(tourFiles, function (tourFile) {
                     angular.forEach(tourFile, function(newTour) {