[cv] simplify code thanks to tricium.
[cv] simplify code thanks to tricium.

R=yiwzhang

Change-Id: Ifc7f07be1baee364946072670aef5077dd5e102f
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/3141428
Reviewed-by: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>
Reviewed-by: Scott Lee <1dcb292530f82960316cb3d87cd67c3f212b79cb@chromium.org>
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go