Comment 6 for bug 1798172

Reviewed: https://review.openstack.org/611337
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=57566f4c8d2929c25e76564883369a7c6eda720a
Submitter: Zuul
Branch: stable/rocky

commit 57566f4c8d2929c25e76564883369a7c6eda720a
Author: Matt Riedemann <email address hidden>
Date: Tue Oct 16 16:23:54 2018 -0400

    Ignore uuid if already set in ComputeNode.update_from_virt_driver

    Change Ia69fabce8e7fd7de101e291fe133c6f5f5f7056a sets the
    ComputeNode.uuid to whatever the virt driver reports if the
    virt driver reports a uuid, like in the case of ironic.

    However, that breaks upgrades for any pre-existing compute
    node records which have a random uuid since ComputeNode.uuid
    is a read-only field once set.

    This change simply ignores the uuid from the virt driver
    resources dict if the ComputeNode.uuid is already set.

    The bug actually shows up in the ironic grenade CI job
    logs in stable/rocky but didn't fail the nova-compute startup
    because ComputeManager._update_available_resource_for_node()
    catches and just logs the error, but it doesn't kill the service.

    Change-Id: Id02f501feefca358d36f39b24d426537685e425c
    Closes-Bug: #1798172
    (cherry picked from commit 498413074d1f11688123b6b592d5c204dc7b5ef2)