[Samba] Create backup DC failed

[Stephen Atkins]

Hello.  I'm getting the following when trying to join my new Samba 
4.14.6 Arch Linux box to the DC.

DsAddEntry failed with status WERR_ACCESS_DENIED info (8567, 
'WERR_DS_INCOMPATIBLE_VERSION')

What I'm trying to do is create a backup DC.  I suspect that it's 
because my current DC is running at function level "Windows Server 2016" 
at a schema version 88.

Just wanted to confirm that this level isn't currently supported before 
I band my head on the wall to much.
-- 
Stephen Atkins