xenapi: nova_instance_uuid not set for root image

[Rick Harris]

In the xenapi driver, VDIs should be annotated with the disk-type and instance-uuid in the `other_config` attribute.

This is used to associate a VDI with an instance so that we can safely remove it in the event that it becomes orphaned (see cleanup_attached_vdis).

Currently this is only being set in `create_vdi`. Unfortunately, doesn't account for root VDIs which are created implicitly by glance-plugin dropping a new VHD into the SR.

The solution is to modify the glance-plugin (or the compute-calling code) to add the other config.

For a cleanup script, we can populate VDI's that are missing this data by finding the sibling 'swap' VDI, and copying that info into the root VDI (changing disk type from swap to root).

Things to account for:

* Thin-provisioned images, does the `use_cow` path handle this?
* Bit-torrented images
* Snapshotted images

[Johannes Erdfelt (johannes.erdfelt)]

I'm a fan of having nova-compute do it in a single code-path instead of spread out across plugins :)

[Rick Harris (rconradharris)]

Can't use swap VDI b/c early instances won't even have that. Instead, we can use name-label which has form 'instance-<UUID>' for us (RAX).

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/25973

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/25973
Committed: http://github.com/openstack/nova/commit/f3843dec216f400417637b145aa2982898f6c0c0
Submitter: Jenkins
Branch: master

commit f3843dec216f400417637b145aa2982898f6c0c0
Author: Rick Harris <email address hidden>
Date: Tue Apr 2 17:48:31 2013 +0000

    xenapi: Always set other_config for VDIs

    The existing code only set `other_config` on a VDI when it was created using
    `create_vdi`. This patch updates the code so that `other_config` is also set
    when a VDI is created from a dom0 plugin or during a migration.

    Also included is a one-time script to set the other_config for existing
    VDIs that were affected by this bug.

    Fixes bug 1162029

    Change-Id: I4fa856754487f77ce9c8e39d45eee7ea5187123e