Avoid extra query when loading port security binding

[Salvatore Orlando]

Plugins supporting the port security extension perform an extra db query for each element being retrieved by get_networks and get_ports operation.

The extra query is performed in the following methods:
_extend_network_port_security_dict: https://github.com/openstack/neutron/blob/master/neutron/db/portsecurity_db.py#L54
_extend_port_port_security_dict: https://github.com/openstack/neutron/blob/master/neutron/db/portsecurity_db.py#L58

Using similar technicques adopted for other API extensions, this extra query, which negatively impacts performance and scalability, should be removed.

This bug affects only the nicira plugin as it is currently the only plugin which enables this ext.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/39093

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/39093
Committed: http://github.com/openstack/neutron/commit/f581b2faf11b49852b0e1d6f2ddd8d19b8b69cdf
Submitter: Jenkins
Branch: master

commit f581b2faf11b49852b0e1d6f2ddd8d19b8b69cdf
Author: Salvatore Orlando <email address hidden>
Date: Mon Jul 15 00:21:12 2013 +0200

    Avoid performing extra query for fetching port security binding

    Bug 1201957

    Add a relationship performing eager load in Port and Network
    models, thus preventing the 'extend' function from performing
    an extra database query.
    Also fixes a comment in securitygroups_db.py

    Change-Id: If0f0277191884aab4dcb1ee36826df7f7d66a8fa