Tools: hv: Add an example script to retrieve DNS entries

To keep the KVP daemon code free of distro specific details, we invoke an
external script to retrieve the DNS entries. This is an example script that
was used to test the KVP code. This script has to be implemented in a Distro
specific fashion. For instance on distros that ship with Network Manager enabled,
this script can be based on NM APIs.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>