Suggest to get rid of netifaces dependency

[liuzhe-lz]

netifaces is hard to build on Windows. It does not provide wheel for latest Python.
This package is used to get IP address of eth0, which should be simply done by hostname -i. eth0 is not preferred by systemd comparing to "predictable" interface name.
Of course hostname is not supported by Windows, but I believe eth0 will not work either.

I think we should be conservative to introduce binary/native dependencies. They will cause installation problem sooner or later.

[J-shang]

This does cause some trouble. It ask me to install visual c++ build tools 2016 with 3GB to install netifaces, when I want to install nni on my laptop with clean dev env.