LU-12756 lnet: Refactor lnet_compare_routes

LU-12756 lnet: Refactor lnet_compare_routes

Restrict lnet_compare_routes() to only comparing the lnet_route
objects passed as arguments. This saves us from doing unecessary
calls to lnet_find_best_lpni_on_net().

Rename lnet_compare_peers to lnet_compare_gw_lpnis to better
reflect what is done by this routine.

Test-Parameters: trivial
Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: I2d7b5dcc2aacb371b21908ceebf2dd6a349fa74c
Reviewed-on: https://review.whamcloud.com/36621
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>