libvirt: Custom disk_bus setting is being lost when migration is reverted

[Vladik Romanovsky]

When migration is being reverted on a host, the default disk_bus setting are lost .

finish_revert_migration() should use image_meta, if it exist, when constructing
the disk_info.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/132913

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/132913
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=c039eb0326690ea45e3770d00b1d397a49a49662
Submitter: Jenkins
Branch: master

commit c039eb0326690ea45e3770d00b1d397a49a49662
Author: Vladik Romanovsky <email address hidden>
Date: Wed Nov 5 12:59:25 2014 -0500

    libvirt: disk_bus setting is being lost when migration is reverted

    finish_revert_migration() should use image_meta, if it exist,
    when constructing the disk_info.

    Closes-Bug: #1389850
    Change-Id: Ia373771eaaad4154a2aa0695bf3878713a68dd9f