BUG/MINOR: mux-h1: Close server connection if input data remains in h1_detach()

BUG/MINOR: mux-h1: Close server connection if input data remains in h1_detach()

With the previous commit 03627245c ("BUG/MEDIUM: mux-h1: Trim excess server data
at the end of a transaction"), we try to avoid to handle junk data coming from a
server as a response. But it only works for data already received. Starting from
the moment a server sends an invalid response, it is safer to close the
connection too, because more data may come after and there is no good reason to
handle them.

So now, when a conn_stream is detached from a server connection, if there are
some unexpected input data, we simply trim them and close the connection
ASAP. We don't close it immediately only if there are still some outgoing data
to deliver to the server.

This patch must be backported to 2.0 and 1.9.