LU-17000 coverity: Fix Logically dead code under lnetctl.c

LU-17000 coverity: Fix Logically dead code under lnetctl.c

This patch fixes Logically dead code reported by
coverity run. This uncovers the missing call
to lustre_lnet_list_peer() to list peer under
old API.

CoverityID: 404746 ("Logically dead code")

Test-Parameters: trivial testlist=sanity-lnet
Fixes: f0be00678c ("LU-9680 lnet: collect data about peer_ni by using Netlink")
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I0659ce403110118697fb8c88ade70f1695509382
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52921
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>