Allow picking TURN/UDP or TURN/TCP in url params

Also, clean up some legacy TURN-related URL parameters that were
obsolete.  You can now specify a HTTP URL for TURN via ts=, but the
previous ts, tp, ss parameters are now defunct.

PTAL @jiayl, @tkchin
With CEOD, we don't use a STUN server, so it is kind of pointless. This also ensures that we fail hard if CEOD is down for some reason, which I think might be better than silently failing for 10% of users