cas: use AddFileWithoutValidation for faster cache addition
cas: use AddFileWithoutValidation for faster cache addition

Bug: 1110569
Change-Id: I8ba49effb4bc2f61cbefe4d445d6ec18098de0c4
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2356065
Commit-Queue: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

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