Changes

scripts/osmotestconfig: fail with trace on 1st err

Make it easier to figure out why osmotestconfig failed, by failing on
the first error instead of running multiple tests and displaying a
failed error count at the end. Raise an error on failure, so we get a
python trace.

Related: OS#6456
Change-Id: I6a243a2474fbfce63aea8e4418be2f4613808270