This doesn't expose --patch_ref in the bot_update recipe_module yet,
though.

Bug: 865882
Change-Id: I26abe59d2f6a8a3dd3945cce0bf13b238a7fffd3
Reviewed-on: https://chromium-review.googlesource.com/1151105
Commit-Queue: John Budorick <jbudorick@chromium.org>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>