Description:
------------
opcache seems broken, plain and simple. The INI settings are the same to PHP 5.5 where the test script worked.

PHP 5.6.10-1+deb.sury.org~trusty+1 (cli)
Copyright (c) 1997-2015 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2015 Zend Technologies
with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2015, by Zend Technologies

When strace'ing we have found that after the stat to test.php working versions issued 

fcntl(3, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl(3, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0

where 

open("/tmp/.ZendSem.amvda2", O_RDWR|O_CREAT|O_EXCL, 0600) = 3

but this more seems a corollary than a cause, still I thought I'll mention it.

Test script:
---------------
<?php

var_dump(opcache_compile_file('test.php'));
var_dump(opcache_is_script_cached("test.php"));
$scripts = opcache_get_status(TRUE);
var_dump($scripts);
?>

test.php can be either empty or just <?php . It also broke https://www.drupal.org/files/issues/2513326_34.patch (but that's a hack) I got a report it working with 5.6.4; I haven't run the reproduction scripts with 5.6.4.