[handler] bug-fix: cookie_cmd() can result in empty 'cookie' header
[handler] bug-fix: cookie_cmd() can result in empty 'cookie' header

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