This makes it so that regardless of what force is set to in the recipe, if you
invoke bot_update.ensure_checkout, it will actually run.

Removal of the force option (and related options) to come shortly.

R=estaab@chromium.org, hinoka@chromium.org, martiniss@chromium.org, tandrii@chromium.org
BUG=643885

Review-Url: https://codereview.chromium.org/2311673002