heimdal: Fix: Too large time skew, client time 1970-01-01T01:00:00

Part of ed549cb0c53f zeroed out a data structure in the resulting code-file
when a TUTCTime type was freed. This part of the patch applies to Heimdal
7.1+ and not our Heimdal 1.5.2.

PR: 267827
Reported by: Peter Much <pmc@citylink.dinoex.sub.org>
Tested by: Peter Much <pmc@citylink.dinoex.sub.org>
Fixes: ed549cb0c53f
MFC after: TBD with philip@