to_xml should be used in post_live_migration_at_destination method

[wangpan]

in the post_live_migration_at_destination method, the to_xml method is called but the return value never be used, and the comment say that the reason is 'the uuid is not included in to_xml() result'.
but I think the uuid is already included in to_xml() result now, so we may refactor post_live_migration_at_destination method and change it to use the correct way to get the xml of migrated instance.

# In case of block migration, destination does not have
# libvirt.xml
disk_info = blockinfo.get_disk_info(CONF.libvirt_type,
                                    instance)
self.to_xml(instance, network_info, disk_info,
            block_device_info, write_to_disk=True)
# libvirt.xml should be made by to_xml(), but libvirt
# does not accept to_xml() result, since uuid is not
# included in to_xml() result.
dom = self._lookup_by_name(instance["name"])
self._conn.defineXML(dom.XMLDesc(0))

[wangpan (hzwangpan)]

the patch is here:
https://review.openstack.org/#/c/67410

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/67410
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=f05a0c486d8478cdea3808108b172b2487b38bf4
Submitter: Jenkins
Branch: master

commit f05a0c486d8478cdea3808108b172b2487b38bf4
Author: Wangpan <email address hidden>
Date: Fri Jan 17 17:41:06 2014 +0800

    libvirt: use to_xml() in post_live_migration_at_destination

    Currently post_live_migration_at_destination use the dumpped
    xml to define a live-migrated instance, and write the libvirt.xml
    with to_xml(), we should keep consistency of these two places.

    Closes-bug: #1231215

    Change-Id: Id98ee3f21fb7a908a318d0f9abec0b740ff9e410