Add full environment to rake gitlab:elastic:index

ee/lib/tasks/gitlab/elastic.rake

@@ -3,7 +3,7 @@
 namespace :gitlab do
   namespace :elastic do
     desc "GitLab | Elasticsearch | Index everything at once"
-    task :index do
+    task index: :environment do
       # UPDATE_INDEX=true can cause some projects not to be indexed properly if someone were to push a commit to the
       # project before the rake task could get to it, so we set it to `nil` here to avoid that. It doesn't make sense
       # to use this configuration during a full re-index anyways.