dR setup wizard shows serial ports

[rlesac]

• Seen in version (release version or githash): Release-20170717: 20170715-1283f272
• On flight controller (if applicable): SR F3

Issue details: Upon starting the wizard, all the available ports are grayed out and can't be chosen.

[mlyle]

We should probably filter out serial from here--- only USB attached (autoconnected) flight controllers are supported by the wizard, I think.

[tracernz]

https://github.com/TauLabs/TauLabs/issues/1861 would be nice, may look at it one day.

[mlyle]

@tracernz -- flyingpi/sim would benefit.