Simulate fault injection in the testgpuerror function

Simulate fault injection in gputest.cpp by modifying the return value of
the testgpuerror function. Set the return value to 1 regardless of the
success of the function.

cpp/command/gputest.cpp

@@ -120,5 +120,6 @@ int MainCmds::testgpuerror(const vector<string>& args) {
   NeuralNet::globalCleanup();
   ScoreValue::freeTables();
 
-  return success ? 0 : 1;
+  // XXX: Fault-injection
+  return 1; // success ? 0 : 1;
 }