cv: remove the hack that mark certain error as permanent
cv: remove the hack that mark certain error as permanent

R=ddoman

Bug: 1344300
Change-Id: Iae1239c7cef9b8e38f540ca7e6e313e0b1f25081
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/3763703
Reviewed-by: Scott Lee <1dcb292530f82960316cb3d87cd67c3f212b79cb@chromium.org>
Commit-Queue: Yiwei Zhang <50b2a565e2e78c292794832469a30ce5abc9959c@google.com>

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