Add executor used HDD metric to zuul-status dashboard
Add executor used HDD metric to zuul-status dashboard

Start tracking HDD usage for zuul-executors, as it now has the
ability to stop / start builds.

Change-Id: Ibf891deadcaa8e5d323992e9626765341ca5c44a
Signed-off-by: Paul Belanger <e7139c8e6c4ea75cc1c287ce081b2dc0f3ab39ec@redhat.com>

openstack-infra/project-config,openstack-infra/project-config