FOS\UserBundle\Model\UserInterface::setConfirmationToken PHP Method

    function setConfirmationToken($confirmationToken);

 protected function onSuccess(UserInterface $user)
 {
     $user->setPlainPassword($this->getNewPassword());
     $user->setConfirmationToken(null);
     $user->setEnabled(true);
     $this->userManager->updateUser($user);
 }