LU-13340 lustre: Support large nids in LCFG_ADD_UUID

LU-13340 lustre: Support large nids in LCFG_ADD_UUID

struct lustre_cfg contains lcfg_nid which is used only for
LCFG_ADD_UUID.  This is not sufficient for large nids.

The LCFG_ADD_UUID config record has room for 4 arbitrary strings only
one of which is used ("node").  So we can use the second string to
store a larger nid.

Specifically: if lcfg_nid is zero, then the second config string
(named "nid") will store the nid in string format.  When a nid with
4-byte address is needed, that will always be stored in lcfg_nid,
never in the config string.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: If08477df677f26e0ff450803e79dde707becde0f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50096
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>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>