import_zend_test.py now executes CLEAN sections properly

import_zend_test.py now executes CLEAN sections properly

Summary: php-src is inconsistent with test's CLEAN section. Sometimes it starts with php open tags sometimes it doesn't.
e.g. https://github.com/facebook/hhvm/blob/master/hphp/test/zend/bad/ext/gd/tests/imagegd_nullbyte_injection.php

Also, php-src doesn't execute the CLEAN section when the test is executed. So all errors will be ignored. set error_reporting to 0 when the CLEAN section begins to ignore all errors as well.

Talked to ptarjan on IRC because my reimport will do stupid things and maybe a really nice oncall will do me the favor and reimport the whole thing? :)

Also PHP 5.6.1 is out, I don't know if it makes sense to start the import of the new version without importing 5.6.0 again.

From what I see from my import this should fix a bunch of bad tests :)
Closes https://github.com/facebook/hhvm/pull/3910

Reviewed By: @ptarjan, @JoelMarcey

Differential Revision: D1597942