PRESUBMIT hook to run a sanity check on any new HostSpecs.

Adds a presubmit hook that runs 'suite_scheduler.py --sanity' if
the current patch contains edits to suite_scheduler.ini or a control file.

TEST=Ran it on current repository, which already contains violations:
     WARNING:root:Increase KernelPerBuildRegression to |num: 2|
BUG=chromium-os:36891

Change-Id: I6970131c8f0968a48fd926ed07c275afbe3d8caf
Reviewed-on: https://gerrit.chromium.org/gerrit/40980
Commit-Queue: Prashanth Balasubramanian <beeps@chromium.org>
Reviewed-by: Prashanth Balasubramanian <beeps@chromium.org>
Tested-by: Prashanth Balasubramanian <beeps@chromium.org>
3 files changed