Updated openstack/openstack
Project: openstack/ceilometer  6557d0e4ecb725727618d136269633afba32dc49

isolate event storage models

move event storage models to event module. this is the first step
to separating metering and event data.

Change-Id: I6d720690a958f5b3accf22db66c830bfa48ed9ae
Partially-Implements: blueprint dedicated-event-db