Add eager-load paths to autoload paths to fix Rake tasks

Rake doesn't respect eager-loading, so to avoid explicit requires we have to
duplicate the eager-load config into the auto-load config.

This backports an EE change made in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3706

config/application.rb

@@ -34,6 +34,10 @@ module Gitlab
     config.generators.templates.push("#{config.root}/generator_templates")
+    # Rake tasks ignore the eager loading settings, so we need to set the
+    # autoload paths explicitly
+    config.autoload_paths = config.eager_load_paths.dup
+
     # Only load the plugins named here, in the order given (default is alphabetical).
     # :all can be used as a placeholder for all plugins not explicitly named.
     # config.plugins = [ :exception_notification, :ssl_requirement, :all ]