tests: fixed mkdir() race condition

Author: dg

tests/bootstrap.php

@@ -16,8 +16,5 @@
 
 // create temporary directory
 define('TEMP_DIR', __DIR__ . '/tmp/' . lcg_value());
-@mkdir(TEMP_DIR, 0777, TRUE); // @ - base directory may already exist
-register_shutdown_function(function () {
-	Tester\Helpers::purge(TEMP_DIR);
-	rmdir(TEMP_DIR);
-});
+@mkdir(dirname(TEMP_DIR));
+@mkdir(TEMP_DIR);