downloading chrome and chromedriver from the cipd packages before running felt test on Linux

This shouldn't have any effect for now in the flutter/engine repo.
After this change is in I'll enable integration test for luci in felt
tool.

Change-Id: Ia4f9dba5539c7f010214441ef3859c78ce4a86a7

Recipe tested with current flutter/engine: https://chromium-swarm.appspot.com/task?id=4c237ba292edf510

Change-Id: Ia4f9dba5539c7f010214441ef3859c78ce4a86a7
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/2700
Reviewed-by: Tong Wu <wutong@google.com>