how to update order status in shopping cart to checkout
This is your problem:

$order = commerce_order_status_update($order, "Checkout: Checkout");


You should be passing the machine name for the status

$order = commerce_order_status_update($order, 'checkout_checkout');


See this API doc page on drupalcontrib.org: http://www.drupalcontrib.org/api/drupal/contributions!commerce!modules!order!commerce_order.module/function/commerce_order_status_update/7