MDL-56898 behat: Go to a non html page to avoid any unwanted ajax calls

After scenario is finished, go to README.txt, so
there is no JS/AJAX calls pending and site is ready
for reset before next scenario

lib/tests/behat/behat_hooks.php

@@ -368,6 +368,29 @@ function($errno, $errstr, $errfile, $errline) {
         $this->resize_window('medium');
     }
 
+    /**
+     * Executed after scenario to go to a page where no JS is executed.
+     * This will ensure there are no unwanted ajax calls from browser and
+     * site can be reset safely.
+     *
+     * @param AfterScenarioScope $scope scope passed by event fired after scenario.
+     * @AfterScenario
+     */
+    public function after_scenario(AfterScenarioScope $scope) {
+        try {
+            $this->wait_for_pending_js();
+            $this->getSession()->visit($this->locate_path('/README.txt'));
+            $this->getSession()->reset();
+        } catch (DriverException $e) {
+            // Try restart session, if DriverException caught.
+            try {
+                $this->getSession()->restart();
+            } catch (DriverException $e) {
+                // Do nothing, as this will be caught while starting session in before_scenario.
+            }
+        }
+    }
+
     /**
      * Wait for JS to complete before beginning interacting with the DOM.
      *