s4:lib/messaging: fix interaction between imessaging_reinit and irpc_destructor

s4:lib/messaging: fix interaction between imessaging_reinit and irpc_destructor

This was missing in commit 0d096931196524a2d1bf59470bc629dc9231131e.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15280

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Sep 18 19:45:56 UTC 2024 on atb-devel-224

(cherry picked from commit a14320461e3abb56f5dacc90ca73bc1143270394)

Autobuild-User(v4-19-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-19-test): Wed Oct  2 15:37:43 UTC 2024 on atb-devel-224