LU-9019 mdd: migrate from jiffies64 to ktime

LU-9019 mdd: migrate from jiffies64 to ktime

The mdd layer uses cfs_time_xxx_64() for 64 bit time percision.
This was written before ktime_t came into existence and it uses
64 bit version of jiffies which can vary between nodes due to
HZ being configurable. This provides a consistent format with
nanosecond precision on any node.

Change-Id: Ibec17227fd70a148c83296e8d1c41668f67e9201
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/28407
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>