Fix bug 26449: Set null for configurable options of parent product whenever it's saved

- Update unit test

Author: tna274

app/code/Magento/ConfigurableProduct/Test/Unit/Plugin/Model/ResourceModel/ProductTest.php

@@ -61,6 +61,7 @@ public function testBeforeSaveConfigurable()
 
         $object->expects($this->once())->method('getTypeId')->will($this->returnValue(Configurable::TYPE_CODE));
         $object->expects($this->once())->method('getTypeInstance')->will($this->returnValue($type));
+        $object->expects($this->once())->method('resetConfigurableOptionsData')->with($object);
 
         $this->model->beforeSave(
             $subject,