Disable update module page with tests.

Remove access to Update module when "Disable Install module and Update module" checked in settings.

Added test cases to cover this change.

Closes #3437724

src/EventSubscriber/DisableAddNewModuleRouteSubscriber.php

@@ -27,8 +27,13 @@ class DisableAddNewModuleRouteSubscriber extends RouteSubscriberBase {
    */
   protected function alterRoutes(RouteCollection $collection) {
     $config = $this->configFactory->get('project_browser.admin_settings');
-    if ($config->get('disable_add_new_module') && $route = $collection->get('update.module_install')) {
-      $route->setRequirement('_access', 'FALSE');
+    if ($config->get('disable_add_new_module')) {
+      if ($installRoute = $collection->get('update.module_install')) {
+        $installRoute->setRequirement('_access', 'FALSE');
+      }
+      if ($updateRoute = $collection->get('update.module_update')) {
+        $updateRoute->setRequirement('_access', 'FALSE');
+      }
     }
   }