LU-9810 lnet: prefer Fast Reg

LU-9810 lnet: prefer Fast Reg

The FastReg memory model has less CPU overhead than the default.
Therefore prefer it if the HW supports it.  This
applies in particular to the MLX4 HW which supports both memory
models.

Seagate-bug-id: MRP-4508
Test-Parameters: trivial
Signed-off-by: Alexey Lyashkov <alexey.lyashkov@seagate.com>
Change-Id: I09a85a3724d78b61a40fe18c72dbcc4a87da3013
Reviewed-on: https://review.whamcloud.com/28278
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>