[resultdb] Fix flake
[resultdb] Fix flake

err variable was shadowed.

R=332b6c56634d0f63001046c664a2370006a02420@chromium.org

Bug: 1042602
Change-Id: Ib13ded58df89a20924bb08290214b662fabcb354
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2003086
Commit-Queue: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>
Commit-Queue: Chan Li <332b6c56634d0f63001046c664a2370006a02420@chromium.org>
Reviewed-by: Chan Li <332b6c56634d0f63001046c664a2370006a02420@chromium.org>
Auto-Submit: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>

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