test_migration_149_mysql can trigger a race

[Sean Dague]

There are now 2 tests in test_migrations that do work on a mysql backend, and they can cause races because of testr as they would both be opperating on the same live database doing migrations at the same time.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/20090

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/20090
Committed: http://github.com/openstack/nova/commit/65b3b443503f993a8001e761b0768fe05c99bf68
Submitter: Jenkins
Branch: master

commit 65b3b443503f993a8001e761b0768fe05c99bf68
Author: Sean Dague <email address hidden>
Date: Sat Jan 19 14:33:04 2013 -0500

    fix mysql race in tests

    because of testr, we can't assume the migrations tests run in
    sequence, so they make run all at the same time. This is fine for
    our in memory sqlite db, but when talking to a real external
    database, not so good.

    Since a second mysql test was added, we started racing on these
    migrations them often hitting at the same time causing random fails
    in gate.

    Fix this by moving all the mysql tests into 1 test function, so we
    won't race.

    Fixes bug #1101874

    Change-Id: I7627f3bd510266c99af018d355f960b352573759