Because of the way glean works, we don't actually need to have a DNS
server setup to boot our images. In this case, it is actually
problematic for centos-7, because glean overwrites our
/etc/resolv.conf file.
Change-Id: Ie81bc593ac3257021e0636b6c111c37e8b87b747
Signed-off-by: Paul Belanger <pabelanger@redhat.com>