Code review comment for lp:~danwent/neutron/ovs-plugin-fixes

One comment, you will notice a change that makes it permissible for multiple ports to have the empty string as an attachment. This was because the CLI actually performs an unplug using the empty string:

def api_unplug_iface(client, *args):
    tid, nid, pid = args
    data = {'port': {'attachment-id': ''}}

However, I actually think it would be cleaner if this happened by setting attachment-id to a null/none value. We should check with Salvatore on this.