MAGETWO-49721: Revert backward incompatible changes related to product modules

 -  Fixed incorrect usage of metadataPool entity

Author: YevSent

app/code/Magento/ConfigurableProduct/Model/Product/Type/Configurable.php

@@ -376,7 +376,7 @@ public function getConfigurableAttributes($product)
             ['group' => 'CONFIGURABLE', 'method' => __METHOD__]
         );
         if (!$product->hasData($this->_configurableAttributes)) {
-            $metadata = $this->metadataPool->getMetadata(ProductInterface::class);
+            $metadata = $this->getMetadataPool()->getMetadata(ProductInterface::class);
             $cacheId =  __CLASS__ . $product->getData($metadata->getLinkField()) . '_' . $product->getStoreId();
             $configurableAttributes = $this->cache->load($cacheId);
             $configurableAttributes = $this->hasCacheData($configurableAttributes);
@@ -615,7 +615,7 @@ public function beforeSave($product)
     public function save($product)
     {
         parent::save($product);
-        $metadata = $this->metadataPool->getMetadata(ProductInterface::class);
+        $metadata = $this->getMetadataPool()->getMetadata(ProductInterface::class);
         $cacheId =  __CLASS__ . $product->getData($metadata->getLinkField()) . '_' . $product->getStoreId();
         $this->cache->remove($cacheId);