BigSwitch plugin raises an exception on re-used port-ids

[Kevin Benton]

When a port is re-created using the same ID or moved to a new host, the port_tracking code in the BigSwitch plugin generates an exception.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/40502

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/40502
Committed: http://github.com/openstack/neutron/commit/967e71c0318606558d866f3853c98e74aa963922
Submitter: Jenkins
Branch: master

commit 967e71c0318606558d866f3853c98e74aa963922
Author: Kevin Benton <email address hidden>
Date: Tue Aug 6 08:19:08 2013 -0700

    Fix BigSwitch plugin to handle device_id re-use in porttracker code

    Updates the BigSwitch port_tracker code to use the sqlalchemy merge method
    instead of the add method for the port location tracking code to avoid primary
     key constraint errors if device-ids are moved or re-used

    Fixes: bug #1208990
    Change-Id: I06065ac888873b00f445d4356b17f084ee38c1ea