LU-6128 lnet: handle lnet_check_routes() errors

LU-6128 lnet: handle lnet_check_routes() errors

After adding a route, lnet_check_routes() is called to ensure that
the route added doesn't invalidate the routing configuration.  If
lnet_check_routes() fails then the route just added, which caused the
current configuration to be invalidated is deleted, and an error
is returned to the user

Signed-off-by: Amir Shehata <amir.shehata@intel.com>
Change-Id: I9b0cc105f97e7ddb0e4549626606c91118ca3ff5
Reviewed-on: http://review.whamcloud.com/13445
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>