HTTP/2: switched back to RST_STREAM with NO_ERROR.

In 8df664ebe037, we've switched to maximizing stream window instead
of sending RST_STREAM.  Since then handling of RST_STREAM with NO_ERROR
was fixed at least in Chrome, hence we switch back to using RST_STREAM.

This allows more effective rejecting of large bodies, and also minimizes
non-payload traffic to be accounted in the next patch.