external gateway modes doesn't work with ML2

[Francois Eleouet]

When ML2 plugin is used, L3 agent won't set SNAT rules between internal networks when used with ML2 plugin.

external gateway modes introduces a new "enable_snat" comlumn to Router DB, but as ML2 plugin was merged right after this extension, it isn't included in alembic migration script [1], so this column won't be present for this plugin. As a consequence, L3 agents won't set-up SNAT rules in neutron routers.

[1]https://github.com/openstack/neutron/blob/master/neutron/db/migration/alembic_migrations/versions/128e042a2b68_ext_gw_mode.py

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/42190

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/42190
Committed: http://github.com/openstack/neutron/commit/62040d03b3b7f02ff7f67ed08e0dc867eef183dc
Submitter: Jenkins
Branch: master

commit 62040d03b3b7f02ff7f67ed08e0dc867eef183dc
Author: Francois Eleouet <email address hidden>
Date: Fri Aug 16 13:24:20 2013 +0200

    Add ext-gw-mode support to ML2

    Closes-Bug: #1212772

    ML2 doesn't support ext-gw-mode, resulting in L3 agents not
    setting-up NAT rules in neutron routers (currently, l3 agents
    will assume enable_snat=false if plugin doesn't provide this
    parameter as described in bug 1212868)

    This patchset adds the support of ext-gw-mode to ML2 plugin.

    In order to support ext-gw-mode alembic migration (as well as
    other potential migrations on plugin dbs), folsom_initial
    migration script is fixed to include ML2 plugin. Otherwise
    databases won't be set-up during migration script (but at
    plugin startup by sqlalchemy), resulting in migration failures.

    Change-Id: I95ec18e0a4f0e5b661f3a5d679c434f18f100fa6