Univention Corporate Server 4.4 erratum 429 (bugfix)

This update addresses the following issues:
* It is now possible to filter out users from synchronization by setting the
  UCR variable `connector/ad/mapping/user/ignorefilter` to an LDAP filter.
  Every user matched by this LDAP filter will be ignored by the connector.
* Fix python library path in `prepare-new-instance`. This fixes the feature
  to synchronize several Active Directory domains with one UCS directory
  service.