CVE-2019-14902 dsdb: Change basis of descriptor module deferred processing to be...

CVE-2019-14902 dsdb: Change basis of descriptor module deferred processing to be GUIDs

We can not process on the basis of a DN, as the DN may have changed in a rename,
not only that this module can see, but also from repl_meta_data below.

Therefore remove all the complex tree-based change processing, leaving only
a tree-based sort of the possible objects to be changed, and a single
stopped_dn variable containing the DN to stop processing below (after
a no-op change).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12497

Signed-off-by: Andrew Bartlett <abartlet@samba.org>