On new Ubuntu 22.04 images, stopping systemd-resolved to get the
dhclient script override resolv.conf doesn't work anymore. I
originally used that hack to avoid introducing a delay which is
needed when running it on TCG.
Keep systemd-resolved running instead, and wait for it to be ready
by retrying to resolve a domain a few times before installing
packages, so that we don't add another ugly delay that might
unnecessarily slow down things even further.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>