Add the basic test case iptable

*A bacis class iptable_base for adding case in the future
*Subcase iptable_remove to check if container's iptable rules removed after stop.

Hmmm, I'm wrong again!  That's really odd, it adds interface + iptables after run returns.  Anyway, here's how I got it waiting in a bit more test-specific way:

    class iptable_remove(iptable_base):
        ...
        def new_netdev(self):
            before = self.sub_stuff['before']
            now = set(self.read_veth_device())
            return len(now - before) > 0

        def run_once(self):
            super(iptable_remove, self).run_once()
            utils.wait_for(self.new_netdev, 10,
                           text="Waiting for new net device(s)")
            ...

I also found another another likely problem:  If you have no iptables rules (i.e. ``policy ACCEPT``) It won't add any rules.  I'm not sure if this is "fixed" in later version or not, I guess we will have to wait and see.