message: test: fix http2_integration_test flake
  Fixes
diff: @@ -830,6 +830,7 @@ TEST_P(Http2IntegrationTest, GrpcRetry) { testGrpcRetry(); }
  // Verify the case where there is an HTTP/2 codec/protocol error with an active stream.
  TEST_P(Http2IntegrationTest, CodecErrorAfterStreamStart) {
  initialize();
  + fake_upstreams_[0]->set_allow_unexpected_disconnects(true);
  codec_client_ = makeHttpConnection(lookupPort("http"));
  // Sends a request.
  