git-cl: use private instead of draft
git-cl: use private instead of draft

The private mode is a better fit for how we want private
(e.g. security-critical) changes to be reviewed. Draft
was simply a placeholder until private was ready for use,
which it now is.

Bug: 721880, 722627
Change-Id: Ib7b76c555437f4ddc7ab2b0e7ce5a9f9ee8be825
Reviewed-on: https://chromium-review.googlesource.com/513243
Commit-Queue: Aaron Gable <bbed39beedae4cdb499af742d2fcd6c63934d93b@chromium.org>
Reviewed-by: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools