Fix for OPENSTACK-1325
Fix for OPENSTACK-1325

Since upstream changed it so that exceptions from update_port_postcommit
are now ignored and the port update returns 200 SUCCESS we have to move to
the precommit stage.

When more testing reveals we introduce transaction issues, we will have to
hack into upstream code to fix things.

Change-Id: Ifd0590407b21fd85bfd2ac2452581cd398f46ee1
Closes-Bug: OPENSTACK-1325

nuagenetworks/nuage-openstack-neutron,naveensan1/nuage-openstack-neutron,nuagenetworks/nuage-openstack-neutron,naveensan1/nuage-openstack-neutron