Don't use stream_socket_shutdown() in socket channel

Summary: I'm not sure if fclose() does everything we need in Zend PHP but this solves all my troubles.

Test Plan:

$ ./lint_mock.php # with 4 both with and without questions

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3157