Fix .../usr.bin/lastcomm/legacy_test:main on i386

The time in the output files was ahead by 3 hours on i386. Fix the incorrect
offset.

Differential Revision: https://reviews.freebsd.org/D7079 (as part of a larger diff)
MFC after: 1 week
PR: 210329
Reported by: asomers
Approved by: re (gjb)
Reviewed by: cem
Sponsored by: EMC / Isilon Storage Division