Read the ports using project vmi link

If _list_optimization_enabled is set to True use project_id as parent id
to get the port list, else use the old way.

This fix is the cherry pick of
https://github.com/Juniper/contrail-neutron-plugin/commit/0e1027ce250e8ca5e8929f00f1f1c5953e7d81ca

Change-Id: I32242cb74e8bb4f7166245096f6f4065b6d6c079
Merge "Read the ports using project vmi link"