MINOR: conn-stream: Force mux to wait for read events if abortonclose is set

When the abortonclose option is enabled, to be sure to be immediately
notified when a shutdown is received from the client, the frontend
conn-stream must be sure the mux will wait for read events. To do so, the
CO_RFL_KEEP_RECV flag is set when mux->rcv_buf() is called. This new flag
instructs the mux to wait for read events, regardless its internal state.

This patch is required to fix abortonclose option for H1 client connections.
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 0f01d0b..43f1a88 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -1321,6 +1321,7 @@
 		 * CS_FL_RCV_MORE on the CS if more space is needed.
 		 */
 		max = channel_recv_max(ic);
+		flags |= ((!conn_is_back(conn) && (si_strm(si)->be->options & PR_O_ABRT_CLOSE)) ? CO_RFL_KEEP_RECV : 0);
 		ret = cs->conn->mux->rcv_buf(cs, &ic->buf, max, flags | (co_data(ic) ? CO_RFL_BUF_WET : 0));
 
 		if (cs->flags & CS_FL_WANT_ROOM)