LU-7977 lnet: Have selftest use proper units (MB/s or MiB/s)

LU-7977 lnet: Have selftest use proper units (MB/s or MiB/s)

lnet-selftest currently reports bandwidth statistics as
MB/s but it is really calculated as MiB/s.

This patch corrects the output to say MiB/s and adds a
new option, "--mbs" to the "lst stat" command to change
the units to MB/s.

Test-Parameters: trivial
Signed-off-by: Doug Oucharek <doug.s.oucharek@intel.com>
Change-Id: Iae8f6ca92b9b0ee00e6307eaf22e5c0791ed323d
Reviewed-on: http://review.whamcloud.com/20891
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Olaf Weber <olaf@sgi.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>