core.js: Failing service runner was not exiting with
code != 0. This change should break the tests but because
they were broken already.

Change-Id: Ia47480f48582a6b68b5c4286ce6116f4196f1b3b
diff --git a/test/services/run-services.js b/test/services/run-services.js
index 8cfb4c0..faf80d2 100644
--- a/test/services/run-services.js
+++ b/test/services/run-services.js
@@ -131,9 +131,14 @@
 };
 
 Runner.prototype.stop = function(cb) {
+
   var runner = this;
   if (runner._stopCalled) {
-    debug('warning: stop called multiple times');
+    var errText = 'stop called multiple times';
+    debug(errText);
+    if (cb) {
+      cb(new Error(errText));
+    }
     return;
   }
   runner._stopCalled = true;