[autotest] revert suite throttling

Undo CL:
https://chromium-review.googlesource.com/#/c/167175
keep stats call and _notify_process_limit_hit.

BUG=chromium:
TEST=suite runn in local setup, unittest
DEPLOY=scheduler

Change-Id: I713b69651fabfb8cbb4f9c1ca3a8605900753bc9
Reviewed-on: https://chromium-review.googlesource.com/174896
Commit-Queue: Dan Shi <dshi@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
4 files changed