ctdb: Fix a stuck cluster lock holder after a delayed leader bcast

ctdb: Fix a stuck cluster lock holder after a delayed leader bcast

If a delayed broadcast by a previous cluster lock holder arrives, the
new legitimate leader will accept this without questioning in
leader_handler(). Without this patch rec->leader will never be
overwritten, and because rec->pnn != rec->leader we'll also never send
out fresh leader broadcasts. And because we hold the cluster lock,
nobody else can step up.

Fix this in the next round of leader broadcast timeout.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=15892
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Martin Schwenke <martin@meltin.net>
Autobuild-User(master): Martin Schwenke <martins@samba.org>
Autobuild-Date(master): Thu Aug  7 02:59:20 UTC 2025 on atb-devel-224

(cherry picked from commit 1a7cfd93432a227a972b34e1eb844134173be7b0)

Autobuild-User(v4-22-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-22-test): Thu Aug 21 08:58:34 UTC 2025 on atb-devel-224