Update nginx config to match GitLab repo

• Add fail_timeout=0; as added in https://github.com/gitlabhq/gitlabhq/commit/25ee53c3aea763f794948947a6f4c4fd422bbf7b & recommended by http://unicorn.bogomips.org/Unicorn/Configurator.html#method-i-timeout when Unicorn is running behind nginx.
• Better match formatting to https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/support/nginx/gitlab-ssl & https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/support/nginx/gitlab

Helps with #328 (closed) (why does https://gitlab.com/gitlab-org/omnibus-gitlab/issues/328 not just resolve to show #328 (closed)?)