Added patches for configuration files.

- `nginx.conf` and `default.conf` are pulled from the source of the
  latest nginx RPM for CentOS 7
- `daemon off;` is still executed at the Dockerfile level to ensure
  that even if the `/etc/nginx/nginx.conf` file is edited or replaced
  or symlinked, the engine will still foreground properly
- Dockerfile relies on `patch` executable and will install it