Currently only unit tests are executed, but other type could be needed
(functional, for example). All tests in ``os_vif``, ``vif_plug_ovs`` and
``vif_plug_linux_bridge`` are moved to ``tests\unit`` folder.
TrivialFix
Change-Id: I3ea64a407b5fa8b23e0c8e656a55524139d1b79f