port update triggered even if sec group did not change

[Salvatore Orlando]

the code at: https://github.com/openstack/neutron/blob/master/neutron/db/securitygroups_rpc_base.py#L73

will trigger a rebind of the security group of the port, as well as instruct the plugin to notify the agent if the port update request has the 'security_groups' attribute.

Actually these operations are not needed if there's no change from the current value for security groups.

This condition is causing a fair amount of port_update notification to be sent to the agent; the DHCP port is updated quite often, and since the plugin function is called from the RPC dispatcher, the security groups attribute is not missing, but is an empty list.
For this reason the notification is then sent every time a DHCP port is updated.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/58597

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/58597
Committed: http://github.com/openstack/neutron/commit/121189401a97e5f471a287c453d7f2013c92477a
Submitter: Jenkins
Branch: master

commit 121189401a97e5f471a287c453d7f2013c92477a
Author: Salvatore Orlando <email address hidden>
Date: Tue Nov 26 09:53:49 2013 -0800

    Rebind security groups only when they're updated

    Update the security port bindings for a port only when they actually
    differ from the stored value.

    This will also avoid sending port_update notifications to the agent
    even if nothing actually changes in the port configuration.

    Closes-Bug: #1255183
    Partial blueprint: neutron-tempest-parallel

    Change-Id: I00c29dc97c46478433fdf08069a884bb78e5cd0a