RingpopHandler: update RelayRequest usage for TChannel 2.7.0
RingpopHandler: update RelayRequest usage for TChannel 2.7.0

esatterwhite/skyring,uber/ringpop-node,uber/ringpop-node,esatterwhite/skyring,uber-node/ringpop-node,uber-node/ringpop-node,Collin-V/ringpop,sasa233/ringpop,uber/ringpop