LU-14655 lnet: Protect lpni deref in lnet_health_check

LU-14655 lnet: Protect lpni deref in lnet_health_check

Discovery thread can modify peer NI/peer net/peer relationship
so we need to be careful when dereferencing the peer NI pointer in
lnet_health_check(). Discovery thread operations under net lock, so
move the peer NI dereference under the net lock which is taken for
incrementing the health stats.

Move some of the other code that is only relevant for messages with a
health status != LNET_MSG_STATUS_OK under the appropriate condition.

HPE-bug-id: LUS-9962
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I3e6763b71bcdc9281f46b79c59e40f939190d468
Reviewed-on: https://review.whamcloud.com/43503
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>