Added $_customerCollection property to Storage class

Author: maxalmonte14

app/code/Magento/CustomerImportExport/Model/ResourceModel/Import/Customer/Storage.php

@@ -48,6 +48,13 @@ class Storage
      */
     private $customerCollectionFactory;
 
+    /**
+     * Customer collection.
+     *
+     * @var \Magento\Customer\Model\ResourceModel\Customer\Collection
+     */
+    private $_customerCollection;
+
     /**
      * @param CustomerCollectionFactory $collectionFactory
      * @param CollectionByPagesIteratorFactory $colIteratorFactory