LU-10391 lnet: only use PUBLIC IP6 addresses for connections

LU-10391 lnet: only use PUBLIC IP6 addresses for connections

IPv6 can have temporary address.  These can be used for short-lives
outgoing connections to increase privacy.  They are not suitable for
long-term connections.

So request that only PUBLIC IPv6 addresses are used when making a
connection.

Test-Parameters: trivial testlist=sanity-lnet
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: I1414d9ea11cd5873438a4c088884cefd7d933c8c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48571
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: jsimmons <jsimmons@infradead.org>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>