Comment 7 for bug 1693576

Reviewed: https://review.openstack.org/469672
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=76d59ebcb9ace58d9364877da25f1aa66fb759d8
Submitter: Jenkins
Branch: stable/newton

commit 76d59ebcb9ace58d9364877da25f1aa66fb759d8
Author: Matt Riedemann <email address hidden>
Date: Thu May 25 15:00:24 2017 -0400

    Handle conflict from neutron when addFloatingIP fails

    Neutron can raise a Conflict exception when attempting
    to associate a floating IP to a server when the fixed
    address is already associated to another floating IP.
    This has always resulted in a 400 response, however, it
    would also trace an ERROR in the nova-api logs, which is
    something we shouldn't be doing for an expected type of
    failure.

    This handles the Conflict in the neutronv2 API client code
    and re-raises an exception that the REST API controller code
    can handle and return as a 400 without the stacktrace in the
    logs.

    Conflicts:
          nova/tests/unit/network/test_neutronv2.py

    NOTE(mriedem): The conflict is due to not having change
    I740c49111bc8e5e76a2fe42b35e8d6c9267e04a2 in Newton.

    Change-Id: I27d3241300f75e2aa79a32348a3843e09123cb10
    Closes-Bug: #1693576
    (cherry picked from commit 452f21183f2f80cc5673ebd3fd3e5daf039caacc)
    (cherry picked from commit cea9f71634a161dc58a0c9a43d44a6e9d12ddc4c)