fix some problems in the perchild MPM

apr_socket_t ptr filled in by apr_os_sock_put() needs to be NULL on
entry to have a new structure allocated

various iov problems were fixed

Submitted by:  Jonas Eriksson <jonas@webkonsulterna.com>
Reviewed by:   Jeff Trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97299 13f79535-47bb-0310-9956-ffa450edef68