fix http ioHandler test mocking (#291)
fix http ioHandler test mocking (#291)

INTERNAL

tensorflow/tfjs-node,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs-node,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs-node,tensorflow/tfjs-node,tensorflow/tfjs,tensorflow/tfjs-node