Updated openstack/openstack
Project: openstack/nova  67f28d21950436fceb1377afb5d685ae8a68075f

Fix migration 147 downgrading with no aggregates

Add some extra bulletproofing to downgrading migration 147 where
there may have been no aggregates.

Change-Id: I6e4aabf4fff462e9ad53083621077ce0e0a80a43