Remove mox from nova/tests/unit/test_iptables_network.py
Remove mox from nova/tests/unit/test_iptables_network.py

Replace stubs.Set() with mock.patch.object

Part of blueprint remove-mox-newton

Change-Id: Id2820d0908a302a05699de74d8e2a8f3bafb4c6d

jianghuaw/nova,klmitch/nova,gooddata/openstack-nova,rajalokan/nova,gooddata/openstack-nova,mahak/nova,rajalokan/nova,mikalstill/nova,Juniper/nova,cloudbase/nova,sebrandon1/nova,jianghuaw/nova,hanlind/nova,mahak/nova,alaski/nova,mikalstill/nova,gooddata/openstack-nova,Juniper/nova,jianghuaw/nova,klmitch/nova,vmturbo/nova,Juniper/nova,cloudbase/nova,cloudbase/nova,rahulunair/nova,alaski/nova,rahulunair/nova,vmturbo/nova,jianghuaw/nova,phenoxim/nova,vmturbo/nova,openstack/nova,Juniper/nova,phenoxim/nova,rajalokan/nova,openstack/nova,klmitch/nova,sebrandon1/nova,sebrandon1/nova,vmturbo/nova,hanlind/nova,klmitch/nova,openstack/nova,hanlind/nova,rahulunair/nova,rajalokan/nova,mahak/nova,gooddata/openstack-nova,mikalstill/nova