Comment 10 for bug 1691602

Reviewed: https://review.openstack.org/578612
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=c8756d5a4a7c06d25705af6243ea8ce8fd148411
Submitter: Zuul
Branch: stable/queens

commit c8756d5a4a7c06d25705af6243ea8ce8fd148411
Author: Matt Riedemann <email address hidden>
Date: Wed May 17 22:48:29 2017 -0400

    Handle network-changed event for a specific port

    It turns out that when Neutron sends the "network-changed"
    event it has a port in scope and can provide the port ID.

    Older versions of Neutron wouldn't send this, but if it's
    provided, we can try to optimize the network info cache
    refresh and scope it to just that single port, rather than
    build the entire cache all over again when the other ports
    in the cache may not have changed at all since the last
    time the cache was refreshed.

    This can be especially beneficial for instances with a
    relatively large number of ports which are being migrated.

    Depends-On: Ifdaef05208d09ddd9587fed6214cf388e5265ba4

    Change-Id: I023b5b1ccb248e68189f62ba0ff75d41093c1f60
    Partial-Bug: #1691602
    (cherry picked from commit 537f480927293755bd6365068c1abd0c80951bad)