HTTP/2: don't send SETTINGS ACK before already queued DATA frames. Previously, SETTINGS ACK was sent immediately upon receipt of SETTINGS frame, before already queued DATA frames created using old SETTINGS. This incorrect behavior was source of interoperability issues, because peers rely on the fact that new SETTINGS are in effect after receiving SETTINGS ACK. Reported by Feng Li. Signed-off-by: Piotr Sikora <piotrsikora@google.com>