LU-13027 lnet: fix route consolidation

LU-13027 lnet: fix route consolidation

After discovery one or more peers can be merged together. Some
of those peers might be gateways. The routes from the gateways
should be transferred to the MR peer. However, if the MR peer
is already a gateway, then we shouldn't add routes to a remote
net for which a route already exists, unless that route is
higher priority or has less number of hops, in which case we
should replace the route with the better one.

Test-parameters: trivial

Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I8790f39a604f4e3d222c1f98c3d28d3dfb03a237
Reviewed-on: https://review.whamcloud.com/36917
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>