BigSwitch: async port create susceptible to deadlock

[Kevin Benton]

In the async port creation function used by the Big Switch plugin and ML2 driver, the calls to _set_port_status are susceptible to the well-known eventlet/mysql deadlock.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/84368

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/84368
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=946c34619d2adfcf4b9b27d6e907167ff8bfe0b2
Submitter: Jenkins
Branch: master

commit 946c34619d2adfcf4b9b27d6e907167ff8bfe0b2
Author: Kevin Benton <email address hidden>
Date: Mon Mar 31 23:32:41 2014 -0700

    BigSwitch: Semaphore on port status update

    Adds a semaphore to the _set_port_status
    function used by the Big Switch ML2 driver and
    plugin. Without it, the async threads are
    susceptible to deadlocking and causing the
    known eventlet/mysql timeout exception.

    Closes-Bug: #1300607
    Change-Id: Ie89213a0bef37f9e7a30945df39c0f1b87a33b82