Fix a strict warning in a test

Given this snippet:

```php
<?php

function takeMyReferencePlease(& $myReference) {
	var_dump($myReference);
}

$a = 'foo';
takeMyReferencePlease($a);

takeMyReferencePlease($b = 'bar');
```

Output for hhvm-3.0.1 - 3.2.0:

```
string(3) "foo"

Strict Warning: Only variables should be passed by reference in /in/ii2iK on line 10
string(3) "bar"
```

Output for 5.1.2 - 5.6.0, php7:

```
string(3) "foo"

Strict Standards: Only variables should be passed by reference in /in/ii2iK on line 10
string(3) "bar"
```
Fix iterators tests

https://github.com/facebook/hhvm/issues/3763
Fix some tests related to FS