Univention Corporate Server 4.2 erratum 81 (bugfix)

This update addresses the following issue(s):
* The permissions of the logfile /var/log/univention/ec2.log have been
  fixed.
* The keywords for the module search on the UMC overview page are now
  localized.
* A crash of the UMC-Server during uninstallation of a module is prevented.
* The UMC-Web-Server falls back to english language in case no language is
  provided in HTTP request, which is the case for clients using UCS 4.1.
  This makes it possible to join UCS 4.1 Appliances into UCS 4.2 domains.