Tools: hv: Gather DNS information

Now, gather DNS information. Invoke an external script (that can be
distro dependent) to gather the DNS information.

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>