Wi-fi testing

We should as part of NSFarm test also Wi-Fi.

The advantage of Wi-Fi is that one card connected to testing PC can be used to connect to any board. Well it also introduces some problems such as that SSIDs used in tests should be randomized so that tests do not interfere.

The design around this should mean that we could arbiter Wi-Fi card in PC in tests and that means that cards won't be linked to exact test target. We can also run tests with all cards. This require of course additional code to manage Wi-Fi device sharing between multiple tests to ensure no collisions.