Used cached value of project count to reduce DB load

Requires gitlab-org/gitlab-ce!5746

Possible fix for gitlab-com/infrastructure#303

CHANGELOG-EE

@@ -6,6 +6,7 @@ v 8.11.0 (unreleased)
   - [Elastic][Fix] Commit search breaks for some URLs on gitlab-ce project
 
 v 8.10.5 (unreleased)
+  - Used cached value of project count to reduce DB load
 
 v 8.10.4
   - Fix available users in userselect dropdown when there is more than one userselect on the page. !604 (Rik de Groot)

app/models/concerns/elastic/repositories_search.rb

@@ -12,7 +12,7 @@ module Elastic
       end
 
       def self.repositories_count
-        Project.count
+        Project.cached_count
       end
 
       def client_for_indexing

app/views/admin/dashboard/index.html.haml

@@ -131,7 +131,7 @@
           %h4 Projects
           .data
             = link_to admin_namespaces_projects_path do
-              %h1= number_with_delimiter(Project.count)
+              %h1= number_with_delimiter(Project.cached_count)
             %hr
             = link_to('New Project', new_project_path, class: "btn btn-new")
       .col-sm-4