DB migration support is missing for Mellanox plugin

[Irena Berezovsky]

Mellanox plugin is missing support in alembic migration files.
The Mellanox plugin works because it creates all tables from models via db.confgure() which does metadata.create_all()

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/66545

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/66545
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=37798b728b66dc199bd63cbbe6124b5bbf951d51
Submitter: Jenkins
Branch: master

commit 37798b728b66dc199bd63cbbe6124b5bbf951d51
Author: Itzik Brown <email address hidden>
Date: Sun Jan 12 14:31:18 2014 +0200

    Migration support for Mellanox Neutron plugin

    Adding initial version before Havana to enable
    migration from Havana and including recent changes
    for IceHouse.

    Closes-Bug: 1265080

    Change-Id: I4b18d6d7eb40a9e3b2f3bceaa750827f3ed7c93d