internal: add doc to tlsConn wrapper for channelz (#2421)
internal: add doc to tlsConn wrapper for channelz (#2421)


stanley-cheung/grpc-go,menghanl/grpc-go,thinkerou/grpc-go,grpc/grpc-go,thinkerou/grpc-go,menghanl/grpc-go,dfawley/grpc-go,stanley-cheung/grpc-go,grpc/grpc-go,dfawley/grpc-go