Remove Keystone from Telemetry reference build binaries before upload.
Remove Keystone from Telemetry reference build binaries before upload.

The reference Chrome builds use binaries originally downloaded from
the chrome-unsigned Google Cloud Storage bucket. Those binaries are
uploaded to Telemetry's own storage bucket, and swarming bots
download them from there. This change modifies them after we download
them from chrome-unsigned and before we upload them to
Telemetry's storage bucket.

Note that python's zipfile module doesn't support symlinks,
so I am starting subprocesses instead.

Bug: chromium:932615
Change-Id: I50360df3705cbac239c591fff6929f89463bce7e
Reviewed-on: https://chromium-review.googlesource.com/c/1479906
Reviewed-by: John Chen <334fbfbb4df7c78f091ea1b77c69ca6ac731a3f3@chromium.org>
Reviewed-by: Simon Hatch <490a224d89645d3fea983d7189ce51bde0a00c1d@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult