Improve calling the cron job queryDR, avoid adding the note 2 times to the order

Issue: OnePay Gateway - For the type return, the
$order->add_order_note() run 2 times #19

woo-viet.php

@@ -145,11 +145,13 @@ class WooViet {
 
 			// Add the action to check the cron job for handling queryDR
 			// It's not possible to add in the class "WooViet_OnePay_Domestic_Hook" because it's NOT always loadded
+			if ( defined( 'DOING_CRON' ) and DOING_CRON ) {
 				$this->WooViet_OnePay_Domestic_Hook = new WooViet_OnePay_Domestic();
 				add_action( 'wooviet_handle_onepay_querydr', array(
 					$this->WooViet_OnePay_Domestic_Hook,
 					'handle_onepay_querydr'
 				), 10, 1 );
+			}
 
 		}