Univention Corporate Server 4.4 erratum 239 (bugfix)

This update addresses the following issues:
* The script "remove_ucs_rejected.py" has been repaired.
  It has been broken via UCS 4.4 erratum 155.
* Objects containing a "?" character in their DN could not be synchronized
  due to a decoding error. The synchronization works now.
* These additional attributes are now synchronized
  between UDM/OpenLDAP and Samba/AD
  unixhome, employeeType, employeeNumber,
  loginShell, title, gidNumber, uidNumber, departmentNumber,
  roomNumber.
  The synchronization of user attributes can now be switched on
  and off via the new UCR-variable
  connector/s4/mapping/user/attributes/ignorelist.
  For updates, the synchonization of these attributes is switched off.
  For new installations, the synchonization of these attributes
  is switched on.
* Samba 4.9 no longer allows the removal of the dBCSPwd (LM hash) attribute.
  The S4 connector now respects this.
* A reject is prevented when trying to add a group which is already
  removed in UCS.
* Fixed access to undefined variable in the sync_krbgt script.
* Unused code has been removed.
* The file /etc/univention/connector/s4/localmapping.py is now included in
  mapping.py to allow adjusting the mapping dynamically. It may contain a
  python function mapping_hook(s4_mapping) which can return a modified
  mapping.
* Stop adding an unlimited number of lock entries for the same object.
* Fixed typo in log message
* Avoid a traceback in case GPO deletes get synchronized to Samba/AD and
  the entryUUID of a subobject is unknown.
* Fix a traceback observed in CI tests, where a computer object had already
  been purged in OpenLDAP and the connector tried to apply the echo operation
  for a prior modification in OpenLDAP.