logging: enable json logging in xds server container (#4885)
logging: enable json logging in xds server container (#4885)


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