I know in magento-1.9 version. sorry for this, if this is helps to you. try with following.
/app/code/core/Mage/Checkout/controllers/OnepageController.php
this file is the actual controller file, but depends up on the payment method extensions it will change with Namespace/Modulename/Checkout/controllers/OnepageController.php
Find function saveOrderAction()
find these lines
$this->getOnepage()->getQuote()->save();
/**
* when there is redirect to third party, we don't want to save order yet.
* we will save the order in return action.
*/
if (isset($redirectUrl)) {
$result['redirect'] = $redirectUrl;
}
$this->getResponse()->setBody(Mage::helper('core')->jsonEncode($result));
comment this line //$this->getOnepage()->getQuote()->save();
and add below codes inside the if condition so the condition will look like ..
if (isset($redirectUrl)) {
$result['redirect'] = $redirectUrl;
$this->getOnepage()->getQuote()->setIsActive(1) ;
}
$this->getOnepage()->getQuote()->save();
$this->getResponse()->setBody(Mage::helper('core')->jsonEncode($result));
This is i have done with the third party Payment extension.