MINOR: stream: use conn_full_close() instead of conn_force_close()

We simply disable tracking before calling it.
diff --git a/src/stream.c b/src/stream.c
index 4ec6283..2e9b95c 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -334,8 +334,10 @@
 		http_end_txn(s);
 
 	/* ensure the client-side transport layer is destroyed */
-	if (cli_conn)
-		conn_force_close(cli_conn);
+	if (cli_conn) {
+		conn_stop_tracking(cli_conn);
+		conn_full_close(cli_conn);
+	}
 
 	for (i = 0; i < s->store_count; i++) {
 		if (!s->store[i].ts)