MAGETWO-55668: Processing PR for bugs

- Code style fixed;

Author: adifucan

app/code/Magento/Backup/Test/Unit/Controller/Adminhtml/Index/RollbackTest.php

@@ -170,7 +170,7 @@ public function testExecuteRollbackDisabled()
             ->willReturn($rollbackAllowed);
         $this->objectManagerMock->expects($this->once())
             ->method('get')
-            ->with('Magento\Backup\Helper\Data')
+            ->with(\Magento\Backup\Helper\Data::class)
             ->willReturn($this->dataHelperMock);
 
         $this->assertSame($this->responseMock, $this->rollbackController->execute());