MINOR: stream_interface: add a pointer to the listener for TARG_TYPE_CLIENT

When the target is a client, it will be convenient to have a pointer to the
original listener so that we can retrieve some configuration information at
the stream interface level.
diff --git a/src/peers.c b/src/peers.c
index c615b3b..0ab2e52 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -1157,7 +1157,7 @@
 	s->si[0].conn.ctrl = NULL;
 	s->si[0].release = NULL;
 	s->si[0].send_proxy_ofs = 0;
-	set_target_client(&s->si[0].target);
+	set_target_client(&s->si[0].target, l);
 	s->si[0].exp = TICK_ETERNITY;
 	s->si[0].flags = SI_FL_NONE;
 	if (s->fe->options2 & PR_O2_INDEPSTR)