Comment 2 for bug 1781179

Reviewed: https://review.openstack.org/581658
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=8b16b53b5b54b2ad8521b6c6c22660fab30e1b0d
Submitter: Zuul
Branch: master

commit 8b16b53b5b54b2ad8521b6c6c22660fab30e1b0d
Author: Kailun Qin <email address hidden>
Date: Thu Jul 12 03:18:23 2018 +0800

    Send update instead of remove for DVR reschedule

    The current "agent remove-add" method to reschedule a router is not
    friendly for DVR. In DVR cases, the old agent may still need to keep the
    router in a non-master role to service any VM ports that exit on that
    host while the new agent handles the master role of the router.

    This patch proposes to send "update" instead of "remove" notification
    for DVR rescheduling, which aligns with the retain_router check in
    remove_router_from_l3_agent as well.

    Closes-Bug: #1781179
    Change-Id: I23431f9f46f72e6bce91f3d1fb0ed328d55930fb