LU-9019 mdt: migrate to 64 bit time

LU-9019 mdt: migrate to 64 bit time

Port the remaining time code from 32 bits to 64 bits.
Replace cfs_time_current_sec() to avoid the overflow
issues in 2038 with ktime_get_real_seconds().

Change-Id: Ia97dbfe00cd90dc6ef04583ba2eb512a8feca8c8
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/28788
Reviewed-by: Quentin Bouget <quentin.bouget@cea.fr>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>