patch for samba_dlz

[Kristján Valur Jónsson]

Please see:  https://github.com/samba-team/samba/pull/124
This is a proposed fix for defect
https://bugzilla.samba.org/show_bug.cgi?id=13214

In summary, the bind_samba9.so dlz  fails to work after the named daemon is
"reloaded", which is done by system housekeeping, such as logrotate.

Various parties have reported this, and a useful workaround is to change
such housekeeping scripts to use "restart" instead.  However, that is not a
proper fix (a workaround), since "reload" dlz zones clearly are expected to
support reload.

Note that this patch effectively reverses
https://github.com/samba-team/samba/commit/34eab45cba6989b66d37c7eb74d97846014ec4eb
but only partially.  The crucial fix in that commit was to use talloc_unlink()
instead of talloc_free() on samdb handle.
Creating the singleton created a different problem, that the dlz became
defunct after the reload.


-- 
Kv,
Kristján Valur Jónsson, RVX