Some database accesses in NEC plugin do not support subtransaction

[Akihiro Motoki]

Some database accesses in NEC plugin did not support subtransaction. There are three type below.

(a) subtransactions=True is not specified.
quantum/plugins/nec/db/nec_plugin_base.py: update_packet_filter()
        with context.session.begin():
            pf_entry = nmodels.PacketFilter(**params)
            context.session.add(pf_entry)

(b) transaction commit is not ensured.
quantum/plugins/nec/nec_plugin.py: update_packet_filter()
        old_pf = super(NECPluginV2, self).get_packet_filter(context, id)
        new_pf = super(NECPluginV2, self).update_packet_filter(context, id,
                                                               packet_filter)

(c) using session.flush(). It works but with session.begin(subtransactions=True) is recommended.
quantum/plugins/nec/db/api.py: add_ofc_item()
        item = model(**params)
        session.add(item)
        session.flush()

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/22979

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/22979
Committed: http://github.com/openstack/quantum/commit/9f6adb4b26e5b79a214cf3a29a4ccab4510df6d9
Submitter: Jenkins
Branch: master

commit 9f6adb4b26e5b79a214cf3a29a4ccab4510df6d9
Author: Akihiro MOTOKI <email address hidden>
Date: Tue Feb 26 16:43:03 2013 +0900

    Make sure all db accesses use subtransaction

    Fixes bug 1133253

    Change-Id: If952eaa919cdc7536023525a397e7a8ce4b425aa