Set *_temp_path location to $ServRoot/

[jirutka]

Linux distributions build nginx with options like --http-client-body-temp-path= to set default location of directories for temporary files under /var/tmp/nginx or /var/lib/nginx. The problem is, when running tests as part of the package build process, these directories are not writtable. Therefore it's needed to override location of these directories in the generated nginx.conf.