Like f6f97d72 - pristine copy from omnibus-gitlab 8.7.9+ce.1-0-gf589ad7

Changes are:

    - database.yml.erb

      * db_sslca option to specify CA for cases when DB is accessed via
        SSL (we do not need it as we access DB over unix:// only)

    - gitconfig.erb

      * turns gc.auto=0

        This is questionable to me. What they needed is to adjust
        warning reporting in git, not completely disable gc.auto and control it
        with their hands from rails.

        context: https://gitlab.com/gitlab-org/gitlab-ce/issues/14357

    - gitlab-rails-config.ru.erb removed

      with unicorn OOM killer settings moved to unicorn.rb. See:

      https://gitlab.com/gitlab-org/omnibus-gitlab/commit/cfbe6c55
      https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/672

    - gitlab.yml.erb

      * +geo_bulk_notify_worker (EE only, we do not use gitlab geo)
      * +repository_archive_cache_worker.cron   (gitlab-ce defaults to "0 * * * *")
        https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3663
      * +update_all_remote_mirrors_worker.cron  (EE only ?)
      * +omniauth.external_providers (we do not use omniauth)
      * +trusted_proxies

        this adds ability to let gitlab know trusted proxies addresses
        from which it can get and trust things like X-Forwarded-For and the
        like.

    - nginx-gitlab-http.conf.erb

      * add support for using nginx's realip module
        (http://nginx.org/en/docs/http/ngx_http_realip_module.html) for
        configuring trusted proxies and letting requests from them to
        pass through nginx with e.g. X-Forwarded-For header.

    - smtp_settings.rb.erb

      * +ssl option

        https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/730

    - unicorn.rb: see above about "gitlab-rails-config.ru.erb removed"

The following files stay the same:

    - gitlab-shell-config.yml.erb
    - nginx.conf.erb
    - rack_attack.rb.erb
    - resque.yml.erb