[autotest] Inform modifiers of suite_scheduler.ini of how to test.

suite_scheduler has the ability to verify its config file and exit.
We should probably mention this in the suite_scheduler.ini file so that
it's not just test lab team lore.

TEST=suite_scheduler -t
BUG=None

Change-Id: Id486e19a60d1d30c747eadb0acb4e785cb3b71b6
Reviewed-on: https://gerrit.chromium.org/gerrit/36479
Tested-by: Alex Miller <milleral@chromium.org>
Reviewed-by: Scott Zawalski <scottz@chromium.org>
Commit-Ready: Alex Miller <milleral@chromium.org>
1 file changed