Update dependency on net-ldap '0.2.2' to '0.4.0' which is released as net-ldap-1

Version 0.4.0 has important fixes of encoding problems when
you try to write UTF-8 data to directory service. It is sad that
it was never released to "official" channel so folks were
forced to push net-ldap-1.
Update Gemfile.lock with updated version of net-ldap