Comment 13 for bug 1732543

Reviewed: https://review.openstack.org/526102
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=9dff53ce65e44a75d953ed9b6c6859184b0995a8
Submitter: Zuul
Branch: stable/pike

commit 9dff53ce65e44a75d953ed9b6c6859184b0995a8
Author: Miguel Lavalle <email address hidden>
Date: Tue Jun 20 23:25:24 2017 +0000

    Move segment deletion back to PRECOMMIT_DELETE

    This essentially reverts commit 12d24abba75ab3b926edbac389437bacc23914dd.

    Making the callback _delete_segments_for_network respond to
    BEFORE_DELETE network event has created some bugs. In one of them,
    it is not possible to delete a routed network, because the segments
    cannot be deleted due to the fact that the associated subnets still
    exist.

    Making _delete_segments_for_network respond to PRECOMMIT_DELETE
    introduces a StaleDataError with the standard attributes of the
    deleted segments. To work around that, network_db is expired and
    read again after notifying the PRECOMMIT_DELETE event in
    delete_network in the DB core plug-in.

    This also fixes an issue where we could delete the segment ID
    of the l3-ha network when deleting a router, leaving all other
    routers non-functioning. Moving this to PRECOMMIT_DELETE fixes
    it since it is done after we have checked that the network is
    not in use and can be deleted.

    Closes-Bug: #1697324
    Closes-Bug: #1732543

    Change-Id: I7c3c4654f183b317647a28d599a538fe460db68f