LU-10707 lnet: revert to cfs_time functions

In 2.10 the entire set of changes to using ktime function is not in
creating a situation where routers consider peers dead, essentially
breaking routing functionality.

Revert the changes that were made to LNet as part of LU-6245.

Signed-off-by: Amir Shehata <amir.shehata@intel.com>
Change-Id: Id0765e8332a8b97167d3a602e6410f5bb6a48137
Reviewed-on: https://review.whamcloud.com/32082


Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>