LYNX-227: Variants loading fix

Author: sivaschenko

app/code/Magento/ConfigurableProductGraphQl/Model/Variant/Collection.php

@@ -152,8 +152,13 @@ private function fetch(ContextInterface $context, array $attributeCodes) : array
 
         /** @var ChildCollection $childCollection */
         $childCollection = $this->childCollectionFactory->create();
+        foreach ($this->parentProducts as $product) {
+            $childCollection->setProductFilter($product);
+        }
         $childCollection->addWebsiteFilter($context->getExtensionAttributes()->getStore()->getWebsiteId());
 
+        $attributeCodes = array_unique(array_merge($this->attributeCodes, $attributeCodes));
+
         $this->collectionProcessor->process(
             $childCollection,
             $this->searchCriteriaBuilder->create(),