As part of the fix for bug 1826419, a prior release note was
deleted and no new release note was added to document the
change in behaviour as a result of upgrading.
Add new release note to detail the behaviour of
{network,conf}.dns_domain with respect to the DHCP agent
post upgrade.
The deleted release note will be restored in the stable
branches where it was removed.
Change-Id: Ic668d64c28cdc1068cb2413b09839a127bad46d3
Related-Bug: 1826419