LU-16106 lnet: allow direct messages regardless of peer NI status

LU-16106 lnet: allow direct messages regardless of peer NI status

If check_routers_before_use is enabled, the router needs to
be pinged before it is used, which is not possible because
its NIs are assumed to be down at start-up. Don't prevent
discovery of the router in this case.

This change allows non-routed traffic to peer NIs with "down"
status.

Lustre-commit: 3345a8a54e89c342a4ce2d8d4bcb04ee919bcd52
Lustre-change: https://review.whamcloud.com/c/48355

Test-Parameters: trivial
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: I36fa60e37ef4f47c82c69855c9b0b80bad8a36f4
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/48669
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>