LU-15512 lnet: Stop discovery on deleted peer NI

LU-15512 lnet: Stop discovery on deleted peer NI

lnet_discover_peer_locked() needs to check whether the peer NI that is
undergoing discovery has been deleted (i.e. its assocaited peer has
LNET_PEER_MARK_DELETED state). Otherwise, we may enter an infinite
loop because this peer will never be considered up to date.

Test-Parameters: trivial testlist=sanity-lnet
Fixes: fd32cd817c ("LU-13895 lnet: Prevent discovery on deleted peer")
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I43d276fc460241c1724c8e30913bb6c5cbb7c8f4
Reviewed-on: https://review.whamcloud.com/46429
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>