Downgrade issue with new ldb 2.0.0

[Andrew Bartlett]

Just a heads-up that we have noticed that we need to write a downgrade
script (like sambaundoguididx) for Samba 4.11 (master) -> 4.10 and
below. 

The symptom (eg on a dbcheck --reindex) is:

Invalid @ATTRIBUTES element for 'accountExpires'
Failed to connect to 'tdb:///usr/local/samba/private/sam.ldb' with
backend 'tdb': Unable to load ltdb cache records for backend 'ldb_tdb
backend'

There is no issue on upgrade, just downgrade.

For non-Samba users of ldb additionally the ORDERED_INTEGER value would
need to be specified in @ATTRIBUTES to opt in to this feature, so this
really only matters for Samba because it auto-upgrades the @ATTRIBUTE
record.

I'll soon write a script which drops the problem record by directly
modifying the ldb, similar to sambaundoguididx.

Andrew Bartlett
-- 
Andrew Bartlett
https://samba.org/~abartlet/
Authentication Developer, Samba Team         https://samba.org
Samba Development and Support, Catalyst IT   
https://catalyst.net.nz/services/samba