remove netifaces dependency of ryu-agent
remove netifaces dependency of ryu-agent

Fixes bug #1203663

This patch removes the netifaces dependency.

Change-Id: I0970ca7d8c92fcd1c3dfaded4a9ce6e82b8c033f

wolverineav/networking-bigswitch,stackforge/networking-bigswitch,stackforge/networking-bigswitch,wolverineav/networking-bigswitch,openstack/networking-bigswitch,openstack/networking-bigswitch