Added a network library dependant on the operating system. Windows
and Linux OS are supported. The library is choosen automatically
depending on Python ``os.name``.
Linux library is based on ``ip`` commands and still relying on
``processutils`` library. Linux implementation can't use ``netifaces``
because this library doesn't provide the needed functionality. [1] will
migrate all ``ip`` commands to ``pyroute2`` library.
Windows library relies on Python's ``netifaces`` library because is
enough for the reduced set of commands used. The only functionality
implemented, to cover the bug resolution, is the device existence
check. New functionalities could be added following, for example,
the Neutron implementation.
[1] https://review.openstack.org/#/c/484386/
Closes-Bug: #1672812
Change-Id: I84e3582135ed02137366c8f55f1dd1e4c115f0b5
e8d102b500