the old protocols are largely untested, mostly unused, and have design problems that make the RPC transition a lot harder, if not impossible. in theory we could ship a transparent protocol-converting proxy that'd isolate the daemon itself from old protocol versions, but that's a lot of code to maintain for presumably little gain or even no gain at all. Change-Id: I4c3f3bb34d39044f6aeb07c10caaf13b8340a220