Univention Corporate Server 4.3 erratum 16 (bugfix)

This update addresses the following issue(s):
* A text referring to the activation of UCS has been updated.
* When the meta data of an App pointed to a setup script but it was missing,
  an error occurred. This has been fixed.
* The data directory is no longer moved to the backup directory during the
  uninstallation of an App.
* The UCR variables ldap/base and ldap/server/.* are passed to Docker Apps.
* File permissions for /etc/machine.secret in app containers have been fixed.