[Samba] 4.7.x -> 4.9.x upgrade

[Gregory Sloop]

So, there's been a fair bit of chatter on the list about upgrades failing. I haven't paid close attention, but IIRC, upgrading from 4.7 to 4.8 or 4.9 caused problems.

So, just to clarify - this is an in-place upgrade that is failing, correct?

Does this apply if, instead of an upgrade, one provisions a new DC on, say, 4.9 and joins it? 
In short, will this allow you to get your DCs to 4.9 by creating new DC's on 4.9, and 
then demote/remove all the 4.7 DC's after the new 4.9 DC's are synced etc?

It's just not clear to me, given the stuff I've seen on the list.

TIA
-Greg