Require authorized user to download diagnostics.zip

Tested manually: before the code change, visiting the zip file URL
successfully generated and downloaded the diagnostics .zip file; after
the fix, the GET now returns " [403  Forbidden] " from an anonymous
window, but generates the .zip file when the admin is logged in.
diff --git a/src/com/google/enterprise/adaptor/Dashboard.java b/src/com/google/enterprise/adaptor/Dashboard.java
index 3e47311..80163dc 100644
--- a/src/com/google/enterprise/adaptor/Dashboard.java
+++ b/src/com/google/enterprise/adaptor/Dashboard.java
@@ -87,7 +87,9 @@
     addFilters(scope.createContext("/rpc", createAdminSecurityHandler(
         rpcHandler, config, sessionManager, secure)));
     addFilters(scope.createContext("/diagnostics-support.zip",
-        new DownloadDumpHandler(config.getFeedName().replace('_', '-'))));
+        createAdminSecurityHandler(new DownloadDumpHandler(
+            config.getFeedName().replace('_', '-')),
+            config, sessionManager, secure)));
     addFilters(scope.createContext("/",
           new RedirectHandler(contextPrefix + "/dashboard")));
   }