s3/smbd: Use after free when iterating smbd_server_connection->connections

s3/smbd: Use after free when iterating smbd_server_connection->connections

Change conn_free() to just use a destructor. We now
catch any other places where we may have forgetten to
call conn_free() - it's implicit on talloc_free(conn).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15128

Based on code from Noel Power <noel.power@suse.com>.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Noel Power <npower@samba.org>
Autobuild-User(master): Noel Power <npower@samba.org>
Autobuild-Date(master): Wed Aug 17 09:54:06 UTC 2022 on sn-devel-184