fix slow migration if port security is disabled

For openstack releaes <= train we need to ensure the ports of the migrating vm are properly plugged before letting it run fast (introduced in 1).

However this issue and our check for the port plugging is only applicable to ports that have port security enabled. Non port security enabled ports can not cause the l2 agent to need a long time to load remote security groups since they do not have any security groups.

We therefor explicitly exclude all non port security ports from our check.