Comment 9 for bug 1666424

Reviewed: https://review.openstack.org/454839
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=4a96b962b560733a90b24ae10290e3d835d448e3
Submitter: Jenkins
Branch: stable/newton

commit 4a96b962b560733a90b24ae10290e3d835d448e3
Author: Kevin Benton <email address hidden>
Date: Fri Feb 3 07:16:33 2017 -0800

    Get rid of delete_subnet method in ML2

    This method has grown to be one of the most hideous methods in
    Neutron. It's well past Icehouse so it's time to address the
    REVISIT and get rid of it entirely. :)

    This patch refactors ML2 and the db_base_plugin_v2 delete_subnet
    method so ML2 can perform its ML2-specific tasks with callbacks
    and db_base_plugin_v2 can handle the rest.

    Backport justification: it solves bug 1672701.

    Conflicts:
          neutron/db/db_base_plugin_v2.py
          neutron/plugins/ml2/plugin.py
          neutron/tests/unit/plugins/ml2/test_plugin.py

    Partial-Bug: #1666424
    Change-Id: Ie29acfbe323b60205ade9d660f7497f5bf4a35ca
    (cherry picked from commit 31fa23d84c9054fb4cfebccef953bf6839698a1d)