Also report (TCP) port number (for the OpenFlow connection) for switches

Right now, the YANG model for switches has an IP address for the switch:
https://git.opendaylight.org/gerrit/gitweb?p=controller.git;a=blob;f=opendaylight/md-sal/model/model-flow-service/src/main/yang/flow-node-inventory.yang;h=fc0eb4cf7220c7428a9977f9eb0232e60750f045;hb=HEAD#l153

However, the IP address is not guaranteed to be unique—especially with mininet. We may want to change the model to also add a port in addition to the IP address so that we have a unique L3 way to address the switch.