Fix SSL breakage due to recent is_closed functionality

We didn't proxy these functions properly in the SSL code.

Change-Id: I000bbb012c38a0dfeb07ec241fdf62b8eec8bbe2
Reviewed-on: http://review.couchbase.org/43161
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>