Revert "[client] use scandir to calculate directory size"
Revert "[client] use scandir to calculate directory size"

This reverts commit 7f2a6d81a08fcf01d08506a7f16d7770764c8e3f.

Reason for revert: has a bug & I want to be sure it doesn't get auto-deployed.

Original change's description:
> [client] use scandir to calculate directory size
> 
> Bug: 985537
> Change-Id: I4e79b55d29f72ee72569b86f64a433c2a04b90ac
> Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/1714687
> Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
> Commit-Queue: Takuto Ikuta <tikuta@chromium.org>

TBR=40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org,vadimsh@chromium.org,a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org,tikuta@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 985537
Change-Id: Ic2ef1001ac68fde2b4b6e0f435b3c60a1e04424f
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/1718739
Reviewed-by: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Reviewed-by: Jao-ke Chin-Lee <5de1a387cc854ff3d04fab3d66d4e77a58511771@chromium.org>
Commit-Queue: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py