Make downtime_check happy

db/migrate/20160713222618_add_usage_ping_to_application_settings.rb

@@ -1,6 +1,8 @@
 class AddUsagePingToApplicationSettings < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
 
+  DOWNTIME = false
+
   def change
     add_column :application_settings, :usage_ping_enabled, :boolean, default: true, null: false
   end