Close Batch Change and marking changesets to also be closed does not close changesets

Created by: mike-r-mclaughlin

Steps to reproduce:

1. Create new batch change against a GitHub repo
2. Apply and publish batch change
3. After some time, close the batch change and check the box that says "also close all open changesets on code hosts"
4. The PRs on GitHub are still open

Expected behavior:

PRs are closed on GitHub

Actual behavior:

PRs are left open