This is needed for release builders to checkout the release tags that
will be created when the buildspec branch/release info is migrated out
to the regular repos.

BUG=825063
R=jbudorick@google.com

Change-Id: I5f0e4cdd94de11c59f9b4a5c11aabea129e81523
Reviewed-on: https://chromium-review.googlesource.com/1036526Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Michael Moss <mmoss@chromium.org>