add user-agent header to template downloader request

Author: sudo87

core/src/main/java/com/cloud/storage/template/HttpTemplateDownloader.java

@@ -125,6 +125,7 @@ private GetMethod createRequest(String downloadUrl) {
         GetMethod request = new GetMethod(downloadUrl);
         request.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, myretryhandler);
         request.setFollowRedirects(followRedirects);
+        request.setRequestHeader("User-Agent", "CloudStack-Agent");
         return request;
     }