replace hardcoded AWS image url with static image url

ghost/admin/app/components/gh-nav-menu.js

@@ -2,7 +2,8 @@ import Ember from 'ember';
 
 const {
     Component,
-    inject: {service}
+    inject: {service},
+    computed
 } = Ember;
 
 export default Component.extend({
@@ -12,8 +13,15 @@ export default Component.extend({
 
     open: false,
 
+    navMenuIcon: computed('ghostPaths.subdir', function () {
+        let url = `${this.get('ghostPaths.subdir')}/ghost/img/ghosticon.jpg`;
+
+        return Ember.String.htmlSafe(`background-image: url(${url})`);
+    }),
+
     config: service(),
     session: service(),
+    ghostPaths: service(),
 
     mouseEnter() {
         this.sendAction('onMouseEnter');

ghost/admin/app/templates/components/gh-nav-menu.hbs

@@ -1,5 +1,5 @@
 {{#gh-dropdown-button tagName="header" class="gh-nav-menu" dropdownName="user-menu"}}
-    <div class="gh-nav-menu-icon" style="background-image: url(https://s3.amazonaws.com/f.cl.ly/items/3I0g431b2b3q00253K1V/d16dc430c9c4f5c09d6ca09be3e5c72fdb21c1ac.png)"></div>
+    <div class="gh-nav-menu-icon" style={{navMenuIcon}}></div>
     <div class="gh-nav-menu-details">
         <div class="gh-nav-menu-details-blog">{{config.blogTitle}}</div>
         <div class="gh-nav-menu-details-user">{{session.user.name}}</div>