libads: change netlogon_pings() behaviour wrt to min_servers parameter

libads: change netlogon_pings() behaviour wrt to min_servers parameter

Currently if a caller passes min_servers=X with X>1, netlogon_pings() will fail
if it can't contact X DCs. This is not really what we want. What we want is: we
want at least one DC, and up to X.

Change implemenentation in that sense and rename the min_servers argument to
wanted_servers to express this behaviour change.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15844

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Wed Aug 13 19:31:10 UTC 2025 on atb-devel-224