LU-12303 lnet: recover health at same rate as dec

LU-12303 lnet: recover health at same rate as dec

When there is a failure to send to or over an interface the
interface's health value is decremented by lnet_health_sensitivity.
Originally, when it recovers the health value goes up by 1.
This patch makes incrementing and decrementing health value
symmetrical, by lnet_health_sensitivity.

In this way if a site wants to stop using and start using an interface
quickly, then it can set lnet_health_sensitivity to a large value
compared to the health value maximum, which is hard coded to 1000.
For example setting lnet_health_sensitivity to 500 will reduce the
health value of an interface to 0 after two failed sends and
reset it to maximum health value after two successful sends.

Test-parameters: trivial

Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: Ib5cedb063d9ccf79c574edac291551f8c94bcce4
Reviewed-on: https://review.whamcloud.com/36920
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>