BUG/MEDIUM: mux-h1: Don't loop on the headers parsing if the read0 was received

BUG/MEDIUM: mux-h1: Don't loop on the headers parsing if the read0 was received

If a server sends part of headers and then close its connection, the mux H1
reamins blocked in an infinite loop trying to read more data to finish the
parsing of the message. The flag CS_FL_REOS is set on the conn_stream. But
because there are some data in the input buffer, CS_FL_EOS is never set.

To fix the bug, in h1_process_input, when CS_FL_REOS is set on the conn_stream,
we also set CS_FL_EOS if the input buffer is empty OR if the channel's buffer is
empty.