LU-13883 lnet: Lookup lpni after discovery

LU-13883 lnet: Lookup lpni after discovery

The lpni for a nid can change as part of the discovery process (see
lnet_peer_add_nid()). As such, callers of lnet_discover_peer_locked()
need to lookup the lpni again after discovery completes to make sure
they get the correct peer.

An exception is lnet_check_routers() which doesn't do anything with
the peer or peer NI after the call to lnet_discover_peer_locked().
If the router list is changed then lnet_check_routers() will already
repeat discovery.

Lustre-change: https://review.whamcloud.com/39747
Lustre-commit: 584d9e46053234d02a3290822317552785e44e76

HPE-bug-id: LUS-9167
Test-Parameters: trivial
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I8bdfcb957e87f65ce65bfad81858a4ce3362298e
Reviewed-on: https://review.whamcloud.com/48294
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>