* Add missing PR to release notes

Add some misssing PRs to the notes.

This will need one more update: new date for the release and I want
include the panic-fix in the forward plugin as well.
Signed-off-by: Miek Gieben <miek@miek.nl>

* Update notes/coredns-1.6.8.md
Co-Authored-By: Chris O'Haver <cohaver@infoblox.com>
Co-authored-by: Chris O'Haver <cohaver@infoblox.com>