title: Rest Builder Client post request with header issue grails
body: <p>I am trying post request with rest client builder.</p>
  
  <p>We have following code</p>
  
  <pre><code>RestBuilder rest = new RestBuilder()
  rest = rest.post("https://api..com/ff/one"){
      header 'x-pushbots-appid', '550de488b4569'
      header 'x-pushbots-secret', 'e6717aea77d'
      contentType "application/json"
      json {
          token ="APA91bG9rUbBPURYejC1uzDLbqUMaeHulCtBNIYUokqV5QUwelLygKi8c5c2kD2lq05DXiiKJEDgH8NGfM6DFGhCETgSuX5kOr"
          platform="1"
          msg ="sarath test from API call"
          sound ="ding"
          badge ="badge"
          payload ="JSON"
      }
  }
  </code></pre>
  
  <p>Postman is giving correct result for this request , while  using rest client builder plugin, response is coming as null.
  I checked in api doc and code looks fine.</p>