verify-makefile usage inconsistent, and broken for drupal.org

drush verify-makefile <filename> should always perform drupal.org specific validation, and yet it only works properly if the --drupal-org option is passed. this inconsistency breaks makefile verification on drupal.org, as the project_verify_package module doesn't pass this option to the command (and should not need to).

attached patch fixes this issue by forcing the --drupal-org option when the verify-makefile command is run.