replace cast() with notification for metering data

[Doug Hellmann]

Passing data to the collector should not use a cast() call, since that implies that the sender knows what the receiver is going to do with the data. We should use a model more like notifications, which send the data without any expectations on the receiver beyond agreeing to what the message format is.

[Doug Hellmann (doug-hellmann)]

This ticket depends on bug #1005935

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/80225

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/80225
Committed: https://git.openstack.org/cgit/openstack/ceilometer/commit/?id=fec77dbc85fed701fdbc3a96bae57e5ae3a705cb
Submitter: Jenkins
Branch: master

commit fec77dbc85fed701fdbc3a96bae57e5ae3a705cb
Author: Mehdi Abaakouk <email address hidden>
Date: Tue Jul 29 12:12:06 2014 +0200

    Permit usage of notifications for metering

    This patch introduces a new publisher that uses notification instead
    of RPC.

    And set it by default.

    Closes bug: #1005933
    Implements blueprint replace-rpc-cast-with-notifications
    Co-Authored-By: Ala Rezmerita <email address hidden>

    Change-Id: Idc40c148ef60d5e1349d30c66ba85691d93c5675