BUG: tcp: option nolinger does not work on backends

Daniel Rankov reported that "option nolinger" is inefficient on backends.
The reason is that it is set on the file descriptor only, which does not
prevent haproxy from performing a clean shutdown() before closing. We must
set the flag on the stream_interface instead if we want an RST to be emitted
upon active close.

src/proto_tcp.c

@@ -267,7 +267,7 @@ int tcp_connect_server(struct stream_interface *si)
 		setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof(one));
 
 	if (be->options & PR_O_TCP_NOLING)
-		setsockopt(fd, SOL_SOCKET, SO_LINGER, &nolinger, sizeof(struct linger));
+		si->flags |= SI_FL_NOLINGER;
 
 	/* allow specific binding :
 	 * - server-specific at first