client: update isolated client
client: update isolated client

https://chromium.googlesource.com/infra/infra/+log/9713d76a9f8196d0b8a062262f7910e5244cfe4d..73da3ad249dac1e8efea8c4d7a1b9c98883b59b6/DEPS

    2020-06-03 71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org downloader: verify hash of downloaded tar file
    2020-06-03 71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org isolatedclient: make network error transient
    2020-06-03 71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org downloader: elaborate error in scheduleTarballJob

Bug: 1045281
Change-Id: I57f0969b17f6704d2d0818c7bf47b8ae8f935c2c
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2228925
Commit-Queue: Ye Kuang <1cd89f22f3967fc3dcb883b53940be4b98ec483f@google.com>
Reviewed-by: Ye Kuang <1cd89f22f3967fc3dcb883b53940be4b98ec483f@google.com>
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

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