running `-nvidia=0` with `-testTranscoder=false` results in an O with no capabilities

Once upon a time you had to run -testTranscoder false if you were going to use Nvidia transcoding on Windows. That appears to have been fixed, hooray!

But I did it anyway:

./livepeer.exe -orchestrator true -transcoder true \
  -network offchain -serviceAddr 192.168.0.49:8935 \
  -nvidia 0 -v 9 -testTranscoder false

and it results in a completely useless O: it reports that it has zero capabilities to do anything whatsoever; Bs will always pass it over during the discovery process. No obvious reason for such a thing to be running at all — I guess it could make reward calls or something.

Minimally we should print a log line for this or crash entirely. But perhaps it's time to remove the testTranscoder flag entirely if it's not useful anymore?