LU-10391 lnet: change lp_primary_nid to struct lnet_nid

LU-10391 lnet: change lp_primary_nid to struct lnet_nid

Change lp_primary_nid in struct lnet_peer to 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: I386e85062257f6f8832ffdf4b9603c0e1c072dae
Reviewed-on: https://review.whamcloud.com/42102
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>