https://gerrit-review.googlesource.com/c/110057/ has been deployed,
so this change can now take advantage of that new API to make
git-cl-description more reliable.

Both the API to add content to a change edit and to publish a
change edit return '204 No Content' on a successful call, but this
API returns 200. It seems likely to me that one or the other will
change, so this calling code accepts both codes for future-proofness.

Bug: gerrit:5099
Change-Id: I14d5323f92c807036f8aa11b314d10706c51dbf5
Reviewed-on: https://chromium-review.googlesource.com/544118
Commit-Queue: Aaron Gable <agable@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>