Fix systemtime setting during installation (#6175, #461526).
Moves setuptime step into earliear stage to create files
with correct timestamp (prevent future timestamp skew after boot).
Includes /usr/share/zoneinfo tree in stage 2 (about 0.7 MB),
it is needed if hw clock is in localtime (for
hwclock --hctosys call).
I expect including zoneifo tree in stage 2 to be controversal,
for more info about where we are with timezone setting
and my rationale, please see
esp. the second part starting with "Dealing with the checking"