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>
diff --git a/scheduler/host_scheduler.py b/scheduler/host_scheduler.py
index 8b56ee4..0be63ae 100644
--- a/scheduler/host_scheduler.py
+++ b/scheduler/host_scheduler.py
@@ -323,6 +323,7 @@
 
 
     def schedule_entry(self, queue_entry):
+        logging.debug('Host_scheduler is scheduling entry: %s', queue_entry)
         if queue_entry.host_id is not None:
             return self._schedule_non_metahost(queue_entry)