Univention Corporate Server 4.1 erratum 386 (bugfix)

This update addresses the following issue(s):
* The LDAP modification list can now be logged in case of a traceback
  if the changes are synchronized from UCS to Active Directory.
* The lookup for the LDAP base DN of the Active Directory server has
  been fixed.
* The AD-Connector can now handle `sync_mode` configuration on a per
  attribute granulatrity.
* The samAccountName sycnhronization for Windows clients has been set
  to write only because a changed samAccountName attribute in Active
  Directory is handled via the CN synchronization.
* The mapping for the MS-Exchange related attribute 'proxyAddresses'
  has been revised to synchonize the OpenLDAP attribute 'mailPrimaryAddress'
  with the default value configured in 'proxyAddresses'.
  In detail:
  1. When reading from Active Directory, the value with
  'SMTP:' prefix is now written to the OpenLDAP attribute
  'mailPrimaryAddress'. Before this update 'mailPrimaryAddress' used
  to be synchronized with the value of the Active Directory 'mail'
  attribute instead. The Active Directory 'mail' attribute has informative
  character.
  2. In the other direction, i.e. writing from OpenLDAP to Active Directory,
  the value of 'mailPrimaryAddress' continues to be written to the 'mail'
  attribute and now additionally gets written into the 'proxyAddresses'
  as default value, i.e. prefixed with 'SMTP:'.
  3. 'smtp:' prefixed values in 'proxyAddresses' continue to be synchronized
  with OpenLDAP 'mailAlternativeAddress'.