LU-9019 lfsck: migrate to 64 bit time

LU-9019 lfsck: migrate to 64 bit time

Replace cfs_time_current_sec() to avoid the overflow
issues in 2038 with ktime_get_real_seconds(). The
reset of the lfsck code can move to time64_t as
well. Handle older lfsck on disk data formats that
contain 32 bit time formats. Newly generated on disk
data will always be 64 bit timestamps.

Change-Id: I1db47af3b9f462c31375f53a6216a095ab4767ad
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/26466
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>