OVSDriver: use MAC from getifaddrs if no OVS_VPORT_ATTR_ADDRESS
OVSDriver: use MAC from getifaddrs if no OVS_VPORT_ATTR_ADDRESS

It looks like OpenVSwitch stopped supporting the OVS_VPORT_ATTR_ADDRESS. But,
IVS seems to depend on that for setting the MAC address of a port and failed.
This caused the controller to assume the port MAC address to be
00:00:00:00:00:00 and use that for the LLDP packet-outs. These LLDPs were
promptly dropped by our Dell switch.

harshsin/ivs,harshsin/ivs,floodlight/ivs,vezril/ivs,vezril/ivs,vezril/ivs,harshsin/ivs,floodlight/ivs,floodlight/ivs,harshsin/ivs