BUG/MINOR: mux-h1: Immediately report H1C errors from h1_snd_buf()

In case an H1 stream tries to send while on error occurred on its underlying
H1 connection, we must report the error. The way the stream-interface is
synchronously notified of the error. It seems to only be a problem on the
2.0. Probably because the scheduling has changed in upper versions. On the
2.0, it prevent the stream to be notified of errors, when for instance, a
payload is found in a response to a HEAD request. Not always though.

This patch must be backported as far as 2.0 because, on 2.0, it should fix the
issue #1101. There is no upstream ID for this commit because on the 2.4, this
fix already exists, it is part of non-backportable commit.
1 file changed