Univention Corporate Server 4.1 erratum 331 (security)

This update addresses the following issue(s):
* incorrect handling of crypto NAK packets my result in denial of service
  (CVE-2016-1547)
* Change the time of an ntpd client or deny service to an ntpd client by
  forcing it to change from basic client/server mode to interleaved
  symmetric mode (CVE-2016-1548)
* Timing attack for authenticated packets (CVE-2016-1550)
* Duplicate IPs on unconfig directives will cause an assertion failure
  (CVE-2016-2516)
* Crafted addpeer with hmode > 7 causes out-of-bounds reference
  (CVE-2016-2518)