LU-2934 lnet: Add LNet Router Priority parameter

This change adds a priority parameter to the route module settings.
This paramter can be >= 0. Like hops, the lower the prioirty number
the higher the priority.  So lower numbered priorities will be
selected over higher numbers.

Signed-off-by: Doug Oucharek <doug.s.oucharek@intel.com>
Change-Id: Idca12ee44ec5e2a896f89c178334363ffdfef4b8
Reviewed-on: http://review.whamcloud.com/5663
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>