MAGETWO-53583: "Use Default" checkbox is checked again after saving empty fields (description, name, etc)

- fixed integration build

Author: vgoncharenko

app/code/Magento/Eav/Model/Entity/Attribute/AbstractAttribute.php

@@ -22,6 +22,11 @@ abstract class AbstractAttribute extends \Magento\Framework\Model\AbstractExtens
 {
     const TYPE_STATIC = 'static';
 
+    /**
+     * Const for empty string value.
+     */
+    const EMPTY_STRING = '';
+
     /**
      * Attribute name
      *
@@ -621,7 +626,7 @@ public function isValueEmpty($value)
         return (is_array($value) && count($value) == 0)
             || $value === null
             || ($value === false && $this->getBackend()->getType() != 'int')
-            || ($value === '' && $this->isInEmptyStringTypes());
+            || ($value === self::EMPTY_STRING && $this->isInEmptyStringTypes());
     }
 
     /**
@@ -632,7 +637,7 @@ public function isValueEmpty($value)
      */
     public function isAllowedEmptyTextValue($value)
     {
-        return $this->isInEmptyStringTypes() && $value === '';
+        return $this->isInEmptyStringTypes() && $value === self::EMPTY_STRING;
     }
 
     /**

dev/tests/integration/testsuite/Magento/Eav/Model/ResourceModel/UpdateHandlerTest.php

@@ -11,12 +11,11 @@
 /**
  * @magentoAppArea adminhtml
  * @magentoAppIsolation enabled
+ * @magentoDbIsolation enabled
  */
 class UpdateHandlerTest extends \PHPUnit_Framework_TestCase
 {
     /**
-     * @magentoAppIsolation enabled
-     * @magentoDbIsolation enabled
      * @covers       \Magento\Eav\Model\ResourceModel\UpdateHandler::execute
      * @magentoDataFixture Magento/Catalog/_files/product_simple.php
      * @dataProvider getAllStoresDataProvider
@@ -51,8 +50,6 @@ public function testExecuteProcessForAllStores($code, $snapshotValue, $newValue,
     }
 
     /**
-     * @magentoAppIsolation enabled
-     * @magentoDbIsolation enabled
      * @covers       \Magento\Eav\Model\ResourceModel\UpdateHandlerTest::execute
      * @magentoDataFixture Magento/Catalog/_files/product_simple.php
      * @magentoDataFixture Magento/Store/_files/second_store.php
@@ -95,8 +92,6 @@ public function testExecuteProcessForCustomStore($code, $snapshotValue, $newValu
     }
 
     /**
-     * @magentoAppIsolation enabled
-     * @magentoDbIsolation enabled
      * @covers       \Magento\Eav\Model\ResourceModel\UpdateHandlerTest::execute
      * @magentoDataFixture Magento/Catalog/_files/product_simple.php
      * @magentoDataFixture Magento/Catalog/_files/dropdown_attribute.php