[autotest] Update test_push script to use gmail API

I will update shadow config and credential file in cbf.

BUG=None
TEST=local run, confirm email is sent.

Change-Id: Id523b1c9cf9a4cf6af706b9663c6a41df13bd1b0
Reviewed-on: https://chromium-review.googlesource.com/262771
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Fang Deng <fdeng@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>
1 file changed