Comment 8 for bug 1824571

Reviewed: https://review.opendev.org/661835
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=62e0bee8206491690bd6b6b72fc38d9694d5083f
Submitter: Zuul
Branch: stable/stein

commit 62e0bee8206491690bd6b6b72fc38d9694d5083f
Author: Miguel Lavalle <email address hidden>
Date: Sun May 26 19:15:25 2019 -0500

    Support multiple external networks in L3 agent

    Change [1] removed the deprecated option external_network_bridge. Per
    commit message in change [2], "l3 agent can handle any networks by
    setting the neutron parameter external_network_bridge and
    gateway_external_network_id to empty". So the consequence of [1] was to
    introduce a regression whereby multiple external networks are not
    supported by the L3 agent anymore.

    This change proposes a new simplified rule. If
    gateway_external_network_id is defined, that is the network that the L3
    agent will use. If not and multiple external networks exist, the L3
    agent will handle any of them.

    [1] https://review.opendev.org/#/c/567369/
    [2] https://review.opendev.org/#/c/59359

    Change-Id: Idd766bd069eda85ab6876a78b8b050ee5ab66cf6
    Closes-Bug: #1824571
    (cherry picked from commit 0b3f5f429d2e495eb78d78d46186092ac735e0d5)