Comment 9 for bug 1755243

Reviewed: https://review.openstack.org/557454
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=da141f0859fe5d7e77cd8fbdd84b59e19ffc7d17
Submitter: Zuul
Branch: stable/queens

commit da141f0859fe5d7e77cd8fbdd84b59e19ffc7d17
Author: Daniel Gonzalez <email address hidden>
Date: Mon Mar 12 17:48:54 2018 +0100

    Fix l3-agent crash on routers without ha_state

    l3-agent checks the HA state of routers when a router is updated.
    To ensure that the HA state is only checked on HA routers the following
    check is performed: `if router.get('ha') and not is_dvr_only_agent`.
    This check should ensure that the check is only performed on
    DvrEdgeHaRouter and HaRouter objects.

    Unfortunately, there are cases where we have DvrEdgeRouter objects
    running on 'dvr_snat' agents. E.g. when deploying a loadbalancer with
    neutron-lbaas in a landscape with 6 network nodes and
    max_l3_agents_per_router set to 3, it may happen that the loadbalancer
    is placed on a network node that does not have a DvrEdgeHaRouter running
    on it. In such a case, neutron will deploy a DvrEdgeRouter object on the
    network node to serve the loadbalancer, just like it would deploy a
    DvrEdgeRouter on a compute node when deploying a VM.

    Under such circumstances each update to the router will lead to an
    AttributeError, because the DvrEdgeRouter object does not have the
    ha_state attribute.

    This patch circumvents the issue by doing an additional check on the
    router object to ensure that it actually has the ha_state attribute.

    Closes-Bug: #1755243
    Change-Id: I755990324db445efd0ee0b8a9db1f4d7bfb58e26
    (cherry picked from commit 8c2dae659a806fdc20331de4b8a917ec3ae0e6f6)