Comment 5 for bug 1457571

Reviewed: https://review.openstack.org/178826
Committed: https://git.openstack.org/cgit/openstack/networking-ovn/commit/?id=9c4560dc9932c9d9dddb4fe70a0b59eb6cec219a
Submitter: Jenkins
Branch: master

commit 9c4560dc9932c9d9dddb4fe70a0b59eb6cec219a
Author: Terry Wilson <email address hidden>
Date: Thu Dec 24 17:57:24 2015 +0530

    Add port 'up' and 'down' notification

    This adds the ability to watch for OVSDB events and take action
    when they match specific conditions.

    This patch handles the Logical_Port.up updates
     - At startup, it catches the initial 'create' events from
       ovsdb server and updates the port status if not in sync.
     - If the Logical_Port.up changes from False to True
       it sets the port status to 'ACTIVE' so that neutron server
       can send 'network-vif-plugged' event to nova.
     - If the Logical_Port.up changes from True to False
       it sets the port status to 'DOWN' so that neutron server
       can send 'network-vif-unplugged' event to nova.

    To ensure that only one neutron-server handles the OVSDB events
    it uses the ovsdb lock.

    When the port is created, it sets the status to 'DOWN' by default.

    Co-Authored-By: Numan Siddique <email address hidden>

    Change-Id: Ib7e1ebbbbd430a46aead2402e8b7543b5d73806e
    Closes-bug: #1457571