[Form] Fixed: Added "validation_groups" option to submit button
Merge branch '2.3'

* 2.3:
  Added sleep() workaround for windows php rename bug
  [HttpKernel] removed unused variable
  [Form] Fixed: Added "validation_groups" option to submit button
  [Process] Fix for #8754 (Timed-out processes are successful)

Conflicts:
	src/Symfony/Component/Form/Tests/Extension/Validator/Type/FormTypeValidatorExtensionTest.php