Comment 3 for bug 1061944

Reviewed: https://review.openstack.org/14068
Committed: http://github.com/openstack/nova/commit/07845ad68f83952bbae36b4b115ff6c433e81fa3
Submitter: Jenkins
Branch: master

commit 07845ad68f83952bbae36b4b115ff6c433e81fa3
Author: Clay Gerrard <email address hidden>
Date: Thu Oct 4 18:50:39 2012 -0500

    Always use bdm in instance_block_mapping on Xen

    It doesn't seem that Xen will set the 'root_device_name' property on
    instances. This is causing instance_block_mapping to return early
    without evaluating the bdm before returning the list of device_names
    in use. I'm not sure why instance_block_mapping does this
    (optimization?) but on Xen at least it seems that it should not.

    Added a check for Xen compute_driver flag in instance_block_mapping to
    "guess" the root_device_name (similarlly to what is done in
    compute.utils for swap and ephemeral).

    fixes bug #1061944

    Change-Id: If5b1a2b7377232c78f0629a3624552ecf6ceb0ee