LU-17379 lnet: parallelize peer discovery via LNetAddPeer

LU-17379 lnet: parallelize peer discovery via LNetAddPeer

Initiate peer discovery via its non-primary NIDs
as they are being added in LNetAddPeer by pretending
that they belong to different peers. This may be
useful if some of the comma-separated NIDs in the
mount command (including the first listed NID) are down.
If discovery is performed in the background and there's
at least one reachable NID in the list, the discovery
will succeed and peer records will get consolidated.

If primary NID locking is enabled, The first NID in the list
provided by Lustre to LNetAddPeer always gets locked as primary:
even if it doesn't get discovered.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: I449cb9898c0242db874555a62fe8099352e913e6
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53933
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>