Nginx updates

Unify formatting of https://github.com/gitlabhq/gitlabhq/blob/master/lib/support/nginx/gitlab, https://github.com/gitlabhq/gitlabhq/blob/master/lib/support/nginx/gitlab-ssl, & https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-cookbooks/gitlab/templates/default/nginx-gitlab-http.conf.erb. Also see https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/242.