Comment 10 for bug 1551958

Reviewed: https://review.openstack.org/321633
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=7130d4c5013e6cc37f3b0861424c7766ad5a66a4
Submitter: Jenkins
Branch: stable/liberty

commit 7130d4c5013e6cc37f3b0861424c7766ad5a66a4
Author: Kevin Benton <email address hidden>
Date: Tue Mar 1 13:49:48 2016 -0800

    L3HA: Do not wrap create/delete in transaction

    This is unsafe when calling ML2 because ML2 assumes that its
    functions will not be called inside of a transaction. This is
    not only an issue for drivers that try to do DB lookups using
    a different session in the post commit operation, but it's a
    big issue for the delete methods.

    The delete subnet and network methods in ML2 have 'while True'
    loops that catch concurrency errors and retry the operation after
    looking up info. If these are called inside a transaction, the
    lookups will contain stale information and it can lead to the
    while True loop never terminating!

    Conflicts:
     doc/source/devref/effective_neutron.rst
     neutron/db/l3_hamode_db.py

    Closes-Bug: #1551958
    Change-Id: I33dc084ed15e5491fdda19da712a746ca87fbc8c
    (cherry picked from commit d1c501cd1d31ed3f859975b40c01cb7aaa06d26d)