talloc: fix strndup group of functions

This bug has been fixed years ago in upstream talloc.

talloc.c

@@ -1421,7 +1421,7 @@ char *talloc_strdup_append_buffer(char *s, const char *a)
 char *talloc_strndup_append(char *s, const char *a, size_t n)
 {
 	if (unlikely(!s)) {
-		return talloc_strdup(NULL, a);
+		return talloc_strndup(NULL, a, n);
 	}
 
 	if (unlikely(!a)) {
@@ -1440,7 +1440,7 @@ char *talloc_strndup_append_buffer(char *s, const char *a, size_t n)
 	size_t slen;
 
 	if (unlikely(!s)) {
-		return talloc_strdup(NULL, a);
+		return talloc_strndup(NULL, a, n);
 	}
 
 	if (unlikely(!a)) {