db migration in NVP plugin creates migration branches

[Akihiro Motoki]

After 2d4431d7bc (Add migration for network bindings in NVP plugin,
https://review.openstack.org/#/c/19709/ )
db migration have branches as follows:
--------------------------------------------------
ubuntu@ostack06:/opt/stack/quantum (master)$ quantum-db-manage \
   --config-file /etc/quantum/quantum.conf \
   --config-file /etc/quantum/plugins/openvswitch/ovs_quantum_plugin.ini history

48b6f43f7471 -> 1d76643bcec4 (head), nvp_netbinding

48b6f43f7471 -> 3cb5d900c5de (head), security_groups
5a875d0e5c -> 48b6f43f7471 (branchpoint), DB support for service types
folsom -> 5a875d0e5c, ryu
None -> folsom, folsom initial database
--------------------------------------------------

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/19930

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/19930
Committed: http://github.com/openstack/quantum/commit/b450b3372c9793196d83301412d1fb90ee78900e
Submitter: Jenkins
Branch: master

commit b450b3372c9793196d83301412d1fb90ee78900e
Author: Akihiro MOTOKI <email address hidden>
Date: Thu Jan 17 22:19:45 2013 +0900

    Fix downgrade revision to make db migration linear

    Fixes bug 1100767

    The recent commit 7999282 creates db migration branches.
    The migration timeline should be linear and this commit fixes it.

    Change-Id: I94e1088352112e8c6ec989a54df83e61797b38c5