jobqueue: use more sensible metric key names

jobqueue: use more sensible metric key names

* Since JobQueue metrics are qualified with 'jobqueue.', don't add a 'job-'
  prefix to each metric.
* Separate the key from the job type with a dot rather than a dash.
* To avoid having a Graphite node that is both a "directory" and a metric, use
  '.all' as a suffix for aggregates.

Change-Id: I2ac604d3c042dbfb0b3a27759800f435ec22041e