Making aggregated stats for roles. Extracting more code to
metering utils, to avoid duplication.
Depends on Ceilometer patch:
https://review.openstack.org/#/c/119803/
Change-Id: I6a9e16e8305ef2d6f14912081059ec93ea0606f1
Extracting common metering functins into utils/metering so
they can be reused in multiple places.
Moving old utils file under utils directory.
Change-Id: Id45b6237a68a894721e1b2051f64192781f02f8f