basic/unit-file: ignore any hidden files immediately

Hidden and backup files cannot be valid unit name (we reject anything
starting with a dot, and we require type suffixes). So let's not iterate
over those at all.

src/basic/unit-file.c

@@ -284,7 +284,7 @@ int unit_file_build_name_map(
                         continue;
                 }
 
-                FOREACH_DIRENT_ALL(de, d, log_warning_errno(errno, "Failed to read \"%s\", ignoring: %m", *dir)) {
+                FOREACH_DIRENT(de, d, log_warning_errno(errno, "Failed to read \"%s\", ignoring: %m", *dir)) {
                         char *filename;
                         _cleanup_free_ char *_filename_free = NULL, *simplified = NULL;
                         const char *suffix, *dst = NULL;