Fix printing of error stack in rtcbot when a test fails via test.fail().

R=andresp@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/28449004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7134 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/tools/rtcbot/test.js

@@ -30,7 +30,7 @@ Test.prototype = {
   },
 
   abort: function (error) {
-    var error = error || new Error("Test aborted");
+    var error = new Error(error || "Test aborted");
     console.log(error.stack);
     process.exit(1);
   },