web: add /{tenant}/jobs route

This change adds the 'job:list' job to the scheduler gearman worker
to expose the tenant jobs list.

This change also adds the /{tenant}/jobs.json endpoint to the zuul-web as well
as a /{tenant}/jobs.html web interface and command line client:
  zuul show jobs $tenant

Change-Id: I950cb6a809a360867b2daccded9a8a45ac46359c
6 files changed