Somehow micr0$0ft made it hard to block unwanted updates for Windows 10, but using a registry script Windows 10 users can block unwanted updates. A similar one can unblock it.
See this reference:
So how do you block unwanted upgrade?
Disabling the Windows Update service works well, except for this piece of micr0$0ft skullduggery. Just remember to put it back to Manual when (and if) you want updates.
There's some discussion in this AskWoody thread on how to stop the forced updates to 1709... So how DO you block the upgrade to Win10 1709
In that thread, Woody has posted a link to an article and script to change (and restore) some registry settings... [Fix] How to Stop Automatic Forced Upgrade to Feature Updates in Windows 10
The make it short, link to download the registry scrips is