Updated openstack/openstack
Project: openstack/nova  970cafb0ccaa0285087692497f7b5ffd518c4e9e
null
Prevent caller from specifying id during Migration.create()

The patch is to remove id when it was set before creating a migration
in objects, and check if the migration exists before it is created.

Related to blueprint icehouse-objects.

Change-Id: I37ff279f5f74d17ce9c173458ff35826fb10f143