interop: set dns as default scheme in interop client (#2165)
interop: set dns as default scheme in interop client (#2165)

this is to allow use of grpclb-in-DNS in the interop client
dfawley/grpc-go,grpc/grpc-go,improbable-io/grpc-go,MakMukhi/grpc-go,thinkerou/grpc-go,menghanl/grpc-go,stanley-cheung/grpc-go,grpc/grpc-go,menghanl/grpc-go,improbable-io/grpc-go,MakMukhi/grpc-go,stanley-cheung/grpc-go,dfawley/grpc-go,thinkerou/grpc-go