[lucicfg] Fix flaky test.
[lucicfg] Fix flaky test.

R=2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org, ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org

Change-Id: Idff0b0e4841dd45c2209daa58ace9255ccf4750c
Reviewed-on: https://chromium-review.googlesource.com/c/1435673
Reviewed-by: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>
Reviewed-by: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>
Commit-Queue: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>

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