finagle: make Thrift/ThriftMux not extend ThriftRichServer
finagle: make Thrift/ThriftMux not extend ThriftRichServer

Problem

Because the Thrift and ThriftMux objects extend ThriftRichServer, it is
possible to create a server using Thrift(Mux).serveIface(...). However,
the default params on the Thrift and ThriftMux objects are client params.
The `serveIface` method creates a server using these client params
(such as the stats receiver) using `serverFromIface` *before* calling `serve`
on a properly configured Thrift/ThriftMux server. This means that the Scrooge-
constructed server has the incorrect client params, while all the filters and
factories above it have the correct server params.

Solution

Make Thrift/ThriftMux not extend ThriftRichServer, and update all instances
of Thrift(Mux).serveIface to Thrift(Mux).server.serveIface

RB_ID=824865
TBR=true

thirstycrow/scrooge,twitter/scrooge,thirstycrow/scrooge,twitter/scrooge,twitter/scrooge,twitter/scrooge,thirstycrow/scrooge,thirstycrow/scrooge,thirstycrow/scrooge