Disabling security.limit_extensions with Ubuntu 10.04

This is for adding support for Ubuntu 10.04.  The [security.limit_extensions](https://bugs.php.net/bug.php?id=60763) was added in with [PHP 5.3.9](https://bugs.php.net/bug.php?id=60763), Ubuntu 10.04 packaged [5.3.2](http://packages.ubuntu.com/lucid/php5).

PS - Ubuntu 10.04 will be EOL in April 2015.  Just trying to add up some backwards compatibility in another cookbook. The only other thing people will need to do is to ensure they set the [:process_manager](https://github.com/yevgenko/cookbook-php-fpm/blob/bd7ac6ca2d47bc8a086364e5cb4cbc24e1ae14d1/templates/default/pool.conf.erb#L97) to `static` or `dynamic`.  The `ondemand` option came in later.