Fix integration test issue with interceptor

I have seen the following error:
```
Property Magento\TestFramework\App\Config\Interceptor::$data does not exist
```
This is because `\Magento\TestFramework\Store\StoreManager::reinitStores` does not take into account that \Magento\TestFramework\App\Config as returned from the ObjectManager might just as well be a `\Magento\TestFramework\App\Config\Interceptor`, in case a plugin on that class exists for example.

To be able to still get the data that is needed for the test, there is the need to test for the implementation of \Magento\Framework\Interception\InterceptorInterface and get the $data property from the parent.

Author: AntonEvers

dev/tests/integration/framework/Magento/TestFramework/Store/StoreManager.php

@@ -5,6 +5,7 @@
  */
 namespace Magento\TestFramework\Store;
 
+use Magento\Framework\Interception\InterceptorInterface;
 use Magento\TestFramework\App\Config;
 use Magento\TestFramework\ObjectManager;
 
@@ -128,6 +129,9 @@ public function reinitStores()
         //In order to restore configFixture values
         $testAppConfig = ObjectManager::getInstance()->get(Config::class);
         $reflection = new \ReflectionClass($testAppConfig);
+        if ($reflection->implementsInterface(InterceptorInterface::class)) {
+            $reflection = $reflection->getParentClass();
+        }
         $dataProperty = $reflection->getProperty('data');
         $dataProperty->setAccessible(true);
         $savedConfig = $dataProperty->getValue($testAppConfig);