Backport Admin menu changes from EE

Using path syntax to include Admin namespace as part of Project
controller menu expansion code, in order to not conflict with same
controller name but in Geo namespace.

app/views/layouts/nav/sidebar/_admin.html.haml

@@ -7,14 +7,14 @@
         .sidebar-context-title
           = _('Admin Area')
     %ul.sidebar-top-level-items
-      = nav_link(controller: %w(dashboard admin projects users groups jobs runners gitaly_servers), html_options: {class: 'home'}) do
+      = nav_link(controller: %w(dashboard admin admin/projects users groups jobs runners gitaly_servers), html_options: {class: 'home'}) do
         = link_to admin_root_path, class: 'shortcuts-tree' do
           .nav-icon-container
             = sprite_icon('overview')
           %span.nav-item-name
             = _('Overview')
         %ul.sidebar-sub-level-items
-          = nav_link(controller: %w(dashboard admin projects users groups jobs runners gitaly_servers), html_options: { class: "fly-out-top-item" } ) do
+          = nav_link(controller: %w(dashboard admin admin/projects users groups jobs runners gitaly_servers), html_options: { class: "fly-out-top-item" } ) do
             = link_to admin_root_path do
               %strong.fly-out-top-item-name
                 = _('Overview')
@@ -23,7 +23,7 @@
             = link_to admin_root_path, title: _('Overview') do
               %span
                 = _('Dashboard')
-          = nav_link(controller: [:admin, :projects]) do
+          = nav_link(controller: [:admin, 'admin/projects']) do
             = link_to admin_projects_path, title: _('Projects') do
               %span
                 = _('Projects')