LU-12678 lnet: use list_first_entry() in lnet/klnds subdir

LU-12678 lnet: use list_first_entry() in lnet/klnds subdir

Convert
  list_entry(foo->next .....)
to
  list_first_entry(foo, ....)

in 'lnet/klnds

In several cases the call is combined with a list_empty() test and
list_first_entry_or_null() is used

Lustre-change: https://review.whamcloud.com/43419
Lustre-commit: 34b57a6f8fcd1bc57c0ba92e299bd39f3baa6cb5

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Mr. NeilBrown <neilb@suse.de>
Change-Id: I3b2b33c3c9284c02e44610614d64a1f84be300a4
Reviewed-on: https://review.whamcloud.com/48244
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>