LU-6322 lfsck: show start/complete time directly

LU-6322 lfsck: show start/complete time directly

It is more easy for the users to use/understand when the LFSCK
was started and/or when the LFSCK completed by showing related
time directly.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ibdacccf1abba6041eaddd6bb5456fb122e9ca994
Reviewed-on: http://review.whamcloud.com/13948
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>