Remove unnecessary post-processing code having no effect; closes #3708 (#3733)

The post-processing code `split('\n').join('\n')` does not change nor check anything

Author: wanseob

test/integration/helpers.js

@@ -269,7 +269,7 @@ function _spawnMochaWithListeners(args, fn, opts) {
 
   mocha.on('close', function(code) {
     fn(null, {
-      output: output.split('\n').join('\n'),
+      output: output,
       code: code,
       args: args
     });