libselinux: Add missing errno setup

Errno is not set to ENOENT when lookup_all() doesn't find any match.

fixes: https://src.fedoraproject.org/tests/selinux/issue/51

Signed-off-by: Richard Filo <rfilo@redhat.com>
Acked-by: Ondrej Mosnacek <omosnace@redhat.com>

libselinux/src/label_file.c

@@ -948,6 +948,8 @@ static const struct spec **lookup_all(struct selabel_handle *rec,
 			goto finish;
 		}
 	}
+	if (!result[0])
+		errno = ENOENT;
 
 finish:
 	free(clean_key);