LU-10391 lnet: change lnet_hdr to store large nids.

LU-10391 lnet: change lnet_hdr to store large nids.

'struct lnet_hdr' now has large-addr nids.  They are converted to
4-byte-addr on transmit, and converted back on receive.

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: Icb333e7b62f8151ad103db0a16aa7685a33071e1
Reviewed-on: https://review.whamcloud.com/43604
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>