Fix installation selection

Fix and remove broken tests

See merge request saburly/wiaas/new-wiaas!67

backend/app/plugins/wiaas/includes/delivery-process/class-wiaas-order-fields.php

@@ -430,9 +430,9 @@ class Wiaas_Order_Fields {
 		            }
 
 		            // installation is already selected
-		            if (!empty($bundle_item->get_meta('wiaas_installation', true))) {
+		            if (!empty($bundle_item->get_meta('_wiaas_installation', true))) {
 
-			            $entry[(string) $field->id] = 'wiaas_installation_' . $order->get_id() . '|' . $bundle_item->get_meta('wiaas_installation', true);
+			            $entry[(string) $field->id] = 'wiaas_installation_' . $order->get_id() . '|' . $bundle_item->get_meta('_wiaas_installation', true);
 
 			            continue;
                     }