Autotest: Add more logging.

Went through the logs and added more logging to mostly _schedule_new_jobs()
and _handle_agents(). _handle_agents is eating up the most time with
sometimes a 5-7 second jump on status updates in scheduler_models.

Also changed the tick debug message to say 'Calling' instead of 'Starting'
to make it easier to grep since there is a 'Starting' state.

BUG=chromium-os:34416
TEST=Ran on my system and completed a job to make sure the scheduler processed
     it correctly.

Change-Id: Ic8f21dd8a8f237b5c5cfbd4e101b9150cdb2a818
Reviewed-on: https://gerrit.chromium.org/gerrit/33234
Commit-Ready: Simran Basi <sbasi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
3 files changed