getinfo.c: reset timecond when clearing session-info variables

Bug: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=705783
Reported-by: Ludovico Cavedon <cavedon@debian.org>
tests: add test1511 to check timecond clean-up

Verifies the timecond fix in commit c49ed0b6c0f