LU-16709 lnet: fix locking multiple NIDs of the MR peer

LU-16709 lnet: fix locking multiple NIDs of the MR peer

If LNetPrimaryNID is called on multiple NIDs of the same node,
as a result of peer discovery it is possible that
the discovered peer is found to contain a NID which is locked
as primary by a different existing peer record.
In this case it is safe to delete one of the peer records,
but the NID which got locked the earliest should be
kept as primary.

This allows for the first NID listed in the mount command's
comma-separated list to stay primary as intended
for the purpose of communicating with Lustre even if peer
discovery succeeded using a different NID of MR peer.

Fixes: aacb16191a ("LU-14668 lnet: Lock primary NID logic")
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: Iec9f8b70053fe24cddee552358500dfad0234b7f