Comment 14 for bug 1564335

Reviewed: https://review.openstack.org/330374
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=71686cdaedab8ea176a98fd760afd3c9af3f6d9d
Submitter: Jenkins
Branch: stable/mitaka

commit 71686cdaedab8ea176a98fd760afd3c9af3f6d9d
Author: Pavel Bondar <email address hidden>
Date: Thu Mar 31 13:20:39 2016 +0300

    Update ml2 delete_subnet to deallocate via ipam

    Previosly during delete_subnet in ml2 plugin ip allocation were removed
    directly from database. This way ipam driver was unaware of this
    deallocation.

    Updated workflow to skip removing ip allocations directly from database.
    Now ips are deallocated during update_port workflow (L1008).

    This resolves issue with dhcp ports left in allocated state on ipam
    provides side. Now they are correctly deallocated via update_port.

    But this patch has next limitation: currently SLAAC allocations can
    not be delete via update_port workflow, so ipam driver is still unaware
    of such deallocations.
    This part of issue is expected to be fixed as separate patch.

    Subnet_in_use check was reworked. Previously it assumed that
    auto-allocated ip are already deleted by the time of this check, but
    with new workflow auto allocated ips are deleted later (on update_port).
    So now this check verifies if there are any user allocated ips instead
    of checking all allocations.

    Partial-Bug: #1564335
    Change-Id: I08d66da8cb57ed88e11ec2b18c8345edfce37d37
    (cherry picked from commit 3a2e41bf703d6721fcfe4d72f9ad5c0565fef42d)