drush_backend_batch_process() ignores user if different than 0

If you execute a drush command that invokes drush_backend_batch_process() as a user other than 0 (i.e. drush -u 1 foo_command) the logged in user will not be passed off to the batch command. This can result in inconsistent batch behavior. Specifically I saw this with a batch process that my custom drush command executed to delete nodes.

I have attached a patch that fixes this issue, but in the meantime anyone that needs to do this can change the way they call drush_backend_batch_process() like this:

<?php
  // ...
  global $user;
  drush_backend_batch_process('batch-process -u ' . $user->uid);
?>