server: ensure that server pid file mem is always freed

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/init.c b/init.c
index e9e49eb..1c37ab9 100644
--- a/init.c
+++ b/init.c
@@ -1985,6 +1985,8 @@
 
 	if (is_backend && backend)
 		return fio_start_server(pid_file);
+	else if (pid_file)
+		free(pid_file);
 
 	if (td) {
 		if (!ret)