Allow regular user to list subnets on shared networks

[Salvatore Orlando]

Current policy configuration prevents regular users for listing subnets on shared network, because the policy is set to admin_or_owner.

It is important for nova (and possibly horizon) integration that a regular user can retrieve information for all subnets on a shared network. By construction all the subnets on a shared network are shared.

This can be achieved by exposing the shared attribute for subnets to the policy engine, and then enforcing resource-based policy which apply distinct rules to shared and private objects, as we do for networks.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/11717

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/11717
Committed: http://github.com/openstack/quantum/commit/3dbaa356b9d0af75f5a4102d3e881ca803c895e2
Submitter: Jenkins
Branch: master

commit 3dbaa356b9d0af75f5a4102d3e881ca803c895e2
Author: Salvatore Orlando <email address hidden>
Date: Tue Aug 21 08:26:24 2012 -0700

    Enable users to list subnets on shared networks

    Fixes bug 1039591

    This patch will enable regular users to list subnets on a shared
    network by exposing the subnet's "shared" attribute to the policy
    engine, and letting it applying different rules if the subnet is
    shared or private.

    Change-Id: If204f1e352c114e16251586c743f5b7fe2d1ad7d