Comment 5 for bug 1370782

Reviewed: https://review.openstack.org/128593
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=9ecc4688c1d619a559e53471fbb95652f3e9c97f
Submitter: Jenkins
Branch: stable/icehouse

commit 9ecc4688c1d619a559e53471fbb95652f3e9c97f
Author: Roman Podoliaka <email address hidden>
Date: Thu Sep 18 03:58:59 2014 +0300

    Fix SecurityGroupExists error when booting instances

    Make sure we properly handle the case when multiple threads check
    and create the default security group, if it hasn't existed yet.
    One thread will succeed and others will fail (we have a unique
    constraint in db to prevent a race condition), so just handle the
    exception to let instance boot proceed.

    Steps to reproduce:

    1) install OpenStack with Rally using DevStack:

        https://github.com/stackforge/rally/tree/master/contrib/devstack

    2) fetch the Rally task:

        http://boris-42.github.io/boot.yaml

    3) run it

        rally -v task start boot.yaml

    Closes-Bug: #1370782

    Conflicts:
            nova/tests/db/test_db_api.py

    Change-Id: I414637a31b0b540fefa6c1314be6e973e2d4a178
    (cherry picked from commit b0e48fdaf7442a665d096bc934306d9517d921f0)