Fix gitaly rspec failures 'too many open files'

lib/gitlab/setup_helper.rb

@@ -43,6 +43,7 @@ module Gitlab
         config[:'gitaly-ruby'] = { dir: File.join(gitaly_dir, 'ruby') } if gitaly_ruby
         config[:'gitlab-shell'] = { dir: Gitlab.config.gitlab_shell.path }
         config[:bin_dir] = Gitlab.config.gitaly.client_path
+        config[:git] = { catfile_cache_size: 5 }
 
         TomlRB.dump(config)
       end