[LU-20023] lnet: mark locked primary peer NI DOWN if removed by discovery

• Type: Bug
• Resolution: Fixed
• Priority: Medium
• Fix Version/s: Lustre 2.18.0
• Labels: Health Multi-Rail lnet
• Severity: 3
• Assignee: Serguei Smirnov
• Reporter: Serguei Smirnov

Description

If discovery removes a peer NI but lnet_peer_del_nid() refuses
deletion (e.g. locked primary), the NI remains present, appears healthy,
and so may still be selected for TX.

Treat this as a discovery-driven DOWN event instead by calling
handle_disc_lpni_health(). This preserves the NI for identity while
preventing its use for transmission.