LU-12678 lnet: Fix some out-of-date comments.

The structures these comments describe have changed or been removed,
but the comments weren't updated at the time.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I342edb56790290a0158d4907a5e775e88361ce08
Reviewed-on: https://review.whamcloud.com/39127
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>