Fixes failing test for JRuby

in JRuby FileUtils do not change
current dir when moving files

railties/test/generators/app_generator_test.rb

@@ -113,6 +113,9 @@ def test_application_name_is_detected_if_it_exists_and_app_folder_renamed
 
     FileUtils.mv(app_root, app_moved_root)
 
+    # make sure we are in correct dir
+    FileUtils.cd(app_moved_root)
+
     generator = Rails::Generators::AppGenerator.new ["rails"], { with_dispatchers: true },
                                                                destination_root: app_moved_root, shell: @shell
     generator.send(:app_const)