BZ#2092808 seems to have been fixed. The first connection to the VPN causes winbind to go offline for some reason, but I don't think it's related to SELinux.
I've added more information to bz#2092808 (the bug report already mentions the issue with testparm).
This does not fully fix BZ#2092808. Invoking smbcontrol works, but testparm is still returning an empty string.
Works fine here (F34, Plasma on X11).
Works fine, and BZ#2092808 does seem to be fixed.