BUG/MEDIUM: mux-h2: Remove H2S from send list if data are sent via 0-copy FF

BUG/MEDIUM: mux-h2: Remove H2S from send list if data are sent via 0-copy FF

When data are sent via the zero-copy data forwarding, in h2_done_ff, we must
be sure to remove the H2 stream from the send list if something is send. It
was only performed if no blocking condition was encountered. But we must
also do it if something is sent. Otherwise the transfer may be blocked till
timeout.

This patch must be backported as far as 2.9.

(cherry picked from commit ded28f6e5c210b49ede7edb25cd4b39163759366)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>