[netemul] Sample integration test -> Sockets

Sample integration test on netemul with separate client and server
running on hermetic environments.

Two hermetic environments are spawned and connected via a virtual
network. Then a client process talks to a server process over two
separate nestack implementations.

TEST: test validates separate netstacks running in different
environments

Change-Id: Ic695aa6639ead3e1b688c9d6ee1b53b182850e6a
7 files changed