fix chunk size accumulation in reverse proxy serialize post 3 test
fix chunk size accumulation in reverse proxy serialize post 3 test

h2o/h2o,devnexen/h2o,yannick/h2o,cwyang/h2o,cwyang/h2o,cwyang/h2o,h2o/h2o,devnexen/h2o,yannick/h2o,devnexen/h2o,devnexen/h2o,h2o/h2o,h2o/h2o,devnexen/h2o,devnexen/h2o,devnexen/h2o,h2o/h2o,yannick/h2o,yannick/h2o,yannick/h2o,yannick/h2o,cwyang/h2o,h2o/h2o,h2o/h2o,cwyang/h2o,h2o/h2o,h2o/h2o,cwyang/h2o,cwyang/h2o,yannick/h2o,devnexen/h2o,yannick/h2o,cwyang/h2o,devnexen/h2o,yannick/h2o