Do not need run _enable_netfilter_for_bridges() for each new device

[yujie]

For a new device, when set security group for it, function prepare_port_filter will be called. Then self._enable_netfilter_for_bridges() will be executed once, which is not needed every time.

    def prepare_port_filter(self, port):
        LOG.debug("Preparing device (%s) filter", port['device'])
        self._remove_chains()
        self._set_ports(port)
        self._enable_netfilter_for_bridges()
        # each security group has it own chains
        self._setup_chains()
        return self.iptables.apply()

We could have a look at _enabled_netfilter_for_bridges first and decide whether to run self._enable_netfilter_for_bridges().

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/371912

[OpenStack Infra (hudson-openstack)]

Change abandoned by Yu Jie (<email address hidden>) on branch: master
Review: https://review.openstack.org/371912

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

Closed due to inactivity. Please feel free to reopen if needed.