ml2: subnetroutes table isn't created during db migrations

[Zang MingJie]

The subnetroutes migration scripts exist before ml2 was introduced, so the table isn't created for ml2

Existing installations are working as they rely on auto-generation for DB schemas.

Therefore the bug can be easily fixed by tweaking existing migrations, as there no need to create a distinct migration for deployments upgrading from earlier releases.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/79277

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/79277
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=3f5931f9b666d5ea238300068a964398588488ae
Submitter: Jenkins
Branch: master

commit 3f5931f9b666d5ea238300068a964398588488ae
Author: Zang MingJie <email address hidden>
Date: Mon Mar 10 16:45:35 2014 +0800

    Fix ml2 db migration of subnetroutes table

    The ml2 db migration path doesn't create subnetroutes table. Therefore
    installations were partially relying on automatic schema generation.

    This patch fixes the migration path.

    Change-Id: I3060dd9538b629ad7277af28008ddde27926dcc4
    Closes-Bug: #1290255