simetbox-openwrt-luci: disable currently broken tests

simetbox-openwrt-luci: disable currently broken tests

* The uptime test is currently being rewritten, and will not
  work on any new SIMETBOX until we deploy the new server code and
  the new client code.  Disable its pane in the web interface to
  avoid misleading reports.

* The CDN tests are not working very well (if at all).  Disable its
  pane in the web interface until it gets a much needed rework.