* mod_ldap: Don't filter subgroups on cn=*

Proposed by: covener
Reviewed by: jim, rjung

Backport of r1528143 from trunk.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1528970 13f79535-47bb-0310-9956-ffa450edef68