use go isolate client in trigger.py
use go isolate client in trigger.py

python client is being deprecated.
I will switch swarming client later.

Tested by
~/chromium/src$ python third_party/angle/scripts/trigger.py -p chromium.tests out/Release base_unittests Ubuntu none

Bug: chromium:1047115
Change-Id: Ibad2bf5ab80b09aadfcd0431fea8c5e97d38655d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2095035
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Reviewed-by: Yuly Novikov <36f5580f63d0a3eacc17e89a61d11e2f646630d2@chromium.org>
Commit-Queue: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle