Fails Synchronizing Large Directories

We have a large directory ~80,000 and have noticed the `loginldap:synchronize-users` stops at 20,000. We presume that is because the LDAP server has a response limit. It looks like the PHP ldap module has a [pagination process ](http://php.net/manual/en/function.ldap-control-paged-result.php) to handle this.

Start by reproducing the issue with the `loginldap:synchronize-users` command and review the PHP LDAP pagination process referenced in the issue. Identify where synchronization stops at 20,000 entries and verify that completion handles directories larger than that limit without omitting users.

Written by the indexing model from the issue text.