RelayRequest: add a default log level for errors
RelayRequest: add a default log level for errors

RyanTech/tchannel,bunnyblue/tchannel,Zirpon/tchannel,benfleis/tchannel,sasa233/tchannel,Zirpon/tchannel,chenwenbin928/tchannel,hustxiaoc/tchannel,chenwenbin928/tchannel,hustxiaoc/tchannel,bunnyblue/tchannel,Zirpon/tchannel,i/tchannel,hustxiaoc/tchannel,savaki/tchannel,i/tchannel,benfleis/tchannel,RyanTech/tchannel,sasa233/tchannel,vanloswang/tchannel,bunnyblue/tchannel,vanloswang/tchannel,savaki/tchannel,vanloswang/tchannel,savaki/tchannel,sasa233/tchannel,chenwenbin928/tchannel,i/tchannel,benfleis/tchannel,RyanTech/tchannel