LU-9019 ofd: migrate to 64 bit time

LU-9019 ofd: migrate to 64 bit time

Change fmd_expire and ofd_fmd_max_age to time64_t fields since we
don't need more than seconds resolution. Move several parts of the
code away from jiffies handling since it can be different across a
set of nodes. We leave l_last_used and the stats timeout code alone
since it affects more than the ofd layer.

Change-Id: I505ad9b1c553bf1769241a5920cf146595a3812c
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/28976
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>