Return error on certificate fingerprint failure

Instead of printing the error to stdout return the error to the user.
This may not be a hard error (as later certificates would have passed)
but it never is good to be in a state where you have certificates in a
broken state.

Resolves #586

examples/ortc-quic/main.go

@@ -73,7 +73,10 @@ func main() {
 		panic(err)
 	}
 
-	quicParams := qt.GetLocalParameters()
+	quicParams, err := qt.GetLocalParameters()
+	if err != nil {
+		panic(err)
+	}
 
 	s := Signal{
 		ICECandidates:  iceCandidates,