LU-10391 lnet: extend rspt_next_hop_nid in lnet_rsp_tracker

LU-10391 lnet: extend rspt_next_hop_nid in lnet_rsp_tracker

rspt_next_hop_nid in 'struct lnet_rsp_tracker' is now
a 'struct lnet_nid'.

Test-Parameters: trivial
Test-Parameters: serverversion=2.12 serverdistro=el7.9 testlist=runtests
Test-Parameters: clientversion=2.12 testlist=runtests
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I1348a05e572782383a2e68eb7a6be514a53b28b8
Reviewed-on: https://review.whamcloud.com/43594
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>