Comment 2 for bug 1553689

Reviewed: https://review.openstack.org/288999
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=284f507adaa2af7691e49327cdfc2baba9268455
Submitter: Jenkins
Branch: master

commit 284f507adaa2af7691e49327cdfc2baba9268455
Author: Kevin Benton <email address hidden>
Date: Sun Mar 6 02:24:14 2016 -0800

    Delay description association proxy construction

    Association proxies cannot be constructed in the mixin because they
    will be shared between all models that inherit from it. This means
    they all share one and it will effectively be broken for all but the
    first to load it.

    This changes it to a declared attr like the others to make sure it's
    not constructed until each model inherits from it.

    Change-Id: I3e1aa21cd02c0f116cc6dee5e0577988ec37f767
    Closes-Bug: #1553689