smbd: Avoid sending 0-sized keys to dbwrap

smbd: Avoid sending 0-sized keys to dbwrap

Start the notification one level below /. Sharing and notifying / for changes
is broken at this moment anyway. When sharing / and someone wants to get
notified for changes under /usr, we store "//usr" as the notify_index key. So
this patch does not break anything that is not broken today, and it avoids a
bogus call to dbwrap_parse_records.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>