Call `do_send_informational` only when in a state in which headers are to be sent, rather than letting itself determine states. This is better because the callers know their state (e.g., if write is inflight or if any headers are available).
Call `do_send_informational` only when in a state in which headers are to be sent, rather than letting itself determine states. This is better because the callers know their state (e.g., if write is inflight or if any headers are available).

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