net: use SIGTERM for terminate

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/engines/net.c b/engines/net.c
index 8087207..1d89db1 100644
--- a/engines/net.c
+++ b/engines/net.c
@@ -1213,7 +1213,7 @@
 
 static void fio_netio_terminate(struct thread_data *td)
 {
-	kill(td->pid, SIGUSR2);
+	kill(td->pid, SIGTERM);
 }
 
 #ifdef CONFIG_LINUX_SPLICE