Made test pessimistic by default

The test result was wrong if, for example, the path was wrong.
The unlink() function being never called, it returned the default true value even if it didn't
remove a file.

htdocs/core/lib/files.lib.php

@@ -832,7 +832,7 @@ function dol_delete_file($file,$disableglob=0,$nophperrors=0,$nohook=0,$object=n
 		$error=0;
 
 		//print "x".$file." ".$disableglob;exit;
-		$ok=true;
+		$ok=false;
 		$file_osencoded=dol_osencode($file);    // New filename encoded in OS filesystem encoding charset
 		if (empty($disableglob) && ! empty($file_osencoded))
 		{