[cv] add missing CONFIG_SERVICE_HOST
[cv] add missing CONFIG_SERVICE_HOST

It's required to fetch configs from luci-config.

Bug: 1358208
Change-Id: Ifaa3418177cb48d330e14478b81ede30f2834565
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/3964953
Commit-Queue: Scott Lee <1dcb292530f82960316cb3d87cd67c3f212b79cb@chromium.org>
Commit-Queue: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>
Reviewed-by: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>
Auto-Submit: Scott Lee <1dcb292530f82960316cb3d87cd67c3f212b79cb@chromium.org>

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