LU-11297 lnet: handle router health off

LU-11297 lnet: handle router health off

Routing infrastructure depends on health infrastructure to manage
route status. However, health can be turned off. Therefore, we need
to enable health for gateways in order to monitor them properly.
Each peer now has its own health sensitivity. When adding a route
the gateway's health sensitivity can be explicitly set from lnetctl
or if not specified then it'll default to 1, thereby turning health
on for that gateway, allowing peer NI recovery if there is a failure.

Test-Parameters: forbuildonly
Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: Ibae33d595e97d0eec432ae8f5d51898ce0776f01
Reviewed-on: https://review.whamcloud.com/33634
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Tested-by: Jenkins