dbwrap_rbt: fix modifying the db during traverse

dbwrap_rbt: fix modifying the db during traverse

We delete and add of records rebalace the tree, but our
traverse code doesn't handle that and skips records
randomly.

We maintain records in a linked list for now
in addition to the rbtree and use that list during
traverse.

This add a bit overhead, but at least it works reliable.
If someone finds a way to do reliable traverse with the
rebalanced tree, we can replace this commit.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11375
BUG: https://bugzilla.samba.org/show_bug.cgi?id=11394

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