backport http://svn.apache.org/viewvc?view=rev&revision=591488

fix pool misuse around mod_ldap's connection cache, previously pconf 
could be used during request processing



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@595664 13f79535-47bb-0310-9956-ffa450edef68