mod_ssl: Ensure that the SSL close notify alert is flushed to the client.

         PR54998.

Submitted By: Tim Kosse <tim.kosse filezilla-project.org>, ylavic
Committed By: ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1601184 13f79535-47bb-0310-9956-ffa450edef68