Since git-cl TBR always sets +1, it does not allow auto-submit where
using +2 score as approval.  Let me make git-cl automatically adjust
to proper score.

Bug: 762425
Change-Id: I71fe1af1b8bf5e68d2509c60e8bf05024b6bdbb7
Reviewed-on: https://chromium-review.googlesource.com/680717Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Yoshisato Yanagisawa <yyanagisawa@chromium.org>