Ensure the packed version of protobuf is used on bot tests.
Ensure the packed version of protobuf is used on bot tests.

R=dsansome@chromium.org
BUG=701274

Review-Url: https://codereview.chromium.org/2751863003

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