init: fix localtime_r not work in /init

init: fix localtime_r not work in /init

There is no ANDROID_ROOT environment variable set in /init so that
localtime_r doesn't work because it cannot find the correct tzdata
file under /system.

NO_REF_TASK
Tested:
1) make sure persist.rtc_local_time is 1
2) make sure sysclktz 1 in init.rc
3) set local time in android and reboot to bios, bios should have
   local time
4) reboot back to android, the system time should be correct in
   local time (even network time sync is not available)

Change-Id: I762b8d9a8923e4a4bf58fcafe347b2708a1c8736