Comment 31 for bug 1944619

Reviewed: https://review.opendev.org/c/openstack/nova/+/836014
Committed: https://opendev.org/openstack/nova/commit/29b94aa34ad954e617c2a0d6df0809765dced188
Submitter: "Zuul (22348)"
Branch: stable/yoga

commit 29b94aa34ad954e617c2a0d6df0809765dced188
Author: Erlon R. Cruz <email address hidden>
Date: Tue Dec 7 17:39:58 2021 -0300

    Fix pre_live_migration rollback

    During the pre live migration process, Nova performs most of the
    tasks related to the creation and operation of the VM in the destination
    host. That is done without interrupting any of the hardware in the source
    host. If the pre_live_migration fails, those same operations should be
    rolled back.

    Currently nova is sharing the _rollback_live_migration for both
    live and pre_live migration rollbacks, and that is causing the source
    host to try to re-attach network interfaces on the source host where
    they weren't actually de-attached.

    This patch fixes that by adding a conditional to allow nova to do
    different paths for migration and pre_live_migration rollbacks.

    Closes-bug: #1944619
    Change-Id: I784190ac356695dd508e0ad8ec31d8eaa3ebee56
    (cherry picked from commit 63ffba7496182f6f6f49a380f3c639fc3ded9772)