logging: log_vty_command_string: Fix undercount of buf alloc size

Change-Id: I7aca0ce3d2981001e8081f7cee0dea3e2aaf8f7c
diff --git a/src/logging.c b/src/logging.c
index 1dfd484..381d303 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -932,7 +932,7 @@
 {
 	struct log_info *info = osmo_log_info;
 	int len = 0, offset = 0, ret, i, rem;
-	int size = strlen("logging level () ()") + 1;
+	int size = strlen("logging level (all|) ()") + 1;
 	char *str;
 
 	assert_loginfo(__func__);