No eslint errors in horizon.heattop.js

Running eslint is effectively useless nowdays because of the
overwhelming number of warnings returned.

This patch fixes the existing "no-use-before-define" errors in the
horizon/static/horizon/js/horizon.heattop.js file.

I've decided to only fix those errors here to keep the patch small, and
not destroy any chance of success by needing to rebase every 5 minutes.
Other fixes will be incoming.

Change-Id: I347a472a0eac2e35df14e48f28403a3b8a243c57
Partial-Bug: #1554824

horizon/static/horizon/js/horizon.heattop.js

@@ -22,6 +22,14 @@
 
 var container = "#heat_resource_topology";
 
+/* NOTE: The structure/architecture of this file (lots of global variables
+ *       being referenced within stand-alone functions) means that
+ *       "no-use-before-define" eslint warnings will be rampant.
+ *       I don't believe there's any plan to overhaul this file, so let's not
+ *       clutter up our eslint output with this file's singluar-but-repeated issue.
+ */
+/* eslint-disable no-use-before-define */
+
 function update(){
   node = node.data(nodes, function(d) { return d.name; });
   link = link.data(links);
@@ -242,6 +250,8 @@ function ajax_poll(poll_time){
   }, poll_time);
 }
 
+/* eslint-disable no-use-before-define */
+
 if ($(container).length){
   var width = $(container).width(),
     height = 500,