Comment 3 for bug 1757292

Reviewed: https://review.openstack.org/555481
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=bb8ba2cf568fda4c5c59352296b758705869fb2f
Submitter: Zuul
Branch: master

commit bb8ba2cf568fda4c5c59352296b758705869fb2f
Author: Matt Riedemann <email address hidden>
Date: Thu Mar 22 17:38:00 2018 -0400

    Teardown networking when rolling back live migration even if shared disk

    Change I2c86989ab7c6593bf346611cde8c043116d55bc5 way back in Essex
    added the "setup_network_on_host" network API calls to the migration
    flows, including rollback_live_migration_at_destination. The initial
    implementation of that method for Quantum (Neutron) was a no-op.

    Change Ib1cc44bf9d01baf4d1f1d26c2a368a5ca7c6ab68 in Newton added the
    Neutron implementation for the setup_networks_on_host method in order
    to track the destination host being migrated to for instances that
    have floating IPs with DVR.

    When rolling back from a live migration failure on the destination host,
    the "migrating_to" attribute in the port binding profile, added in
    pre_live_migration() on the destination compute, is cleared.

    However, that only happens in rollback_live_migration_at_destination,
    which is only called if the instance is not on shared storage (think
    libvirt with the rbd image backend or with NFS). That's controlled
    via the "do_cleanup" flag returned from _live_migration_cleanup_flags().

    If the live migration is happening over shared storage and fails, then
    rollback_live_migration_at_destination isn't called which means
    setup_network_on_host isn't called, which means the "migrating_to"
    attribute in the port binding profile isn't cleaned up.

    This change simply adds the cleanup in _rollback_live_migration in the
    event that neutron is being used and we're live migrating over shared
    storage so rollback_live_migration_at_destination isn't called.

    Change-Id: I658e0a749e842163ed74f82c975bcaf19f9f7f07
    Closes-Bug: #1757292