Notification with volume and snapshot metadata

Notification with volume and snapshot metadata

Now notify message to ceilometer do not contain volume
metadata/glance_metadata and snapshot metadata, which are
useful to bill and enrich resource information in ceilometer.

This feature will add the metadata/glance_metadata of volume
and metadata of snapshot to notification usage info.

Change-Id: I04097be9f2da1d6bc45a2d5770bcd543a3f41887
Implements: blueprint notification-with-volume-and-snapshot-metadata