NoopFirewallDriver results in infinite loop with libvirt

[Isaku Yamahata]

 NoopFirewallDriver::instance_filter_exists must return True
 Otherwise, virt.libvirt.connection.ensure_filtering_rules_for_instance() results in infinite loop.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/5270

[Isaku Yamahata (yamahata)]

The patch is uploaded at
https://review.openstack.org/#change,5270

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/5270
Committed: http://github.com/openstack/nova/commit/7c50652a97fe7ebd74ce38572cbd9744c76b2f71
Submitter: Jenkins
Branch: master

commit 7c50652a97fe7ebd74ce38572cbd9744c76b2f71
Author: Isaku Yamahata <email address hidden>
Date: Mon Mar 5 16:21:41 2012 +0900

    virt/firewall: NoopFirewallDriver::instance_filter_exists must return True

    Otherwise, virt.libvirt.connection.ensure_filtering_rules_for_instance()
    results in infinite loop.
    And eliminate NullFirewallDriver as it's same to NoopFirewallDriver.
    This patch fixes bug 953781.

    Change-Id: I7936b3c69e9269041defd1ef7e5dda2de1f96dab