Fix mod_ldap to open an existing shared memory file should one

already exist.
PR: 12757
Obtained from:
Submitted by:	Scooter Morris <scooter@gene.com>
Reviewed by:	Graham Leggett


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@98415 13f79535-47bb-0310-9956-ffa450edef68