Univention Corporate Server 4.2 erratum 50 (bugfix)

This update addresses the following issues:
* The package univention-samba is now also downloaded
  while preparing an appliance.
* A cleanup script used in Univention App Appliances has
  been adapted for UCS 4.2.
* IP address changes are now also applied to portal entries.
* When selecting fast demo mode in an App Appliance, all IP
  addresses in LDAP are reconfigured to the correct address.
* The overview of changed network settings doesn't show HTML code anymore.
* The decision between joining systems into UCS or Active Directory domains
  was confusing and has been improved.
* A crash is prevented when trying to join into an active directory domain
  and the active directory server is not reachable.
* A crash is prevented in appliance scenarios if no domain name was entered.