Fix session references in toolbar and menubar

IPython/html/static/notebook/js/maintoolbar.js

@@ -117,7 +117,7 b' define(['
                     label : 'Interrupt',
                     icon : 'fa-stop',
                     callback : function () {
-                        that.notebook.session.interrupt_kernel();
+                        that.notebook.kernel.interrupt();
                         }
                 },
                 {

IPython/html/static/notebook/js/menubar.js

@@ -287,7 +287,7 b' define(['
         
         // Kernel
         this.element.find('#int_kernel').click(function () {
-            that.notebook.session.interrupt_kernel();
+            that.notebook.kernel.interrupt();
         });
         this.element.find('#restart_kernel').click(function () {
             that.notebook.restart_kernel();