[swarming] Log identity for all the swarming handlers
[swarming] Log identity for all the swarming handlers

Bug: 894045
Change-Id: Ib69e8156af376bda5e66d3c9a6e31a36eb0035b1
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-py/+/2265624
Commit-Queue: Ye Kuang <1cd89f22f3967fc3dcb883b53940be4b98ec483f@google.com>
Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Auto-Submit: Ye Kuang <1cd89f22f3967fc3dcb883b53940be4b98ec483f@google.com>
Reviewed-by: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

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