job-queue-size

aaron sschulz requested that we use the JobQueueGroup::singleton()->getQueueSizes() in addition
to the Config::$job_throttle to avoid flooding a queue. optimized version which was implemented
is JobQueueGroup::singleton()->get( <job queue name> )->getSize().

Change-Id: I8033874cfa0dd0880914672cb5a9b3a7bd526fbe