FIX: Concurently loading deferred loading of a script incorrectly resolves the promise.

app/assets/javascripts/discourse/lib/load-script.js.es6

@@ -37,7 +37,10 @@ export default function loadScript(url, opts) {
 
   $('script').each((i, tag) => {
     const src = tag.getAttribute('src');
-    if (src) _loaded[tag.getAttribute('src')] = true;
+
+    // For some reason, a script tag with `url` as the source is appended into
+    // the head tag while loading the script. 
+    if (src && src !== url) _loaded[tag.getAttribute('src')] = true;
   });