Fix the redirect in the review reply draft resource.

The redirect was passing the wrong variable to get_href(), causing an
HTTP 500 on access. This fixes the variable.
Fix a regression in saving comments.

The new delayed notifications for "change" events from MarkdownEditor
could result in text being chopped off if typing and saving within half
a second. We now make sure to always set the latest-and-greatest text
when saving, instead of relying on the handler for the "change" event.

This only occurs in the comment dialog.

Reviewed at https://reviews.reviewboard.org/r/6457/