Configuration of systemd-resolved does not behave as documented in docs/dns-stack.md

[onock]

Environment:

• Cloud provider or hardware configuration:
  3 KVM-VMs for k8s-leader
  2 KVM-VMs for k8s-worker
  no cloud provider

• OS (printf "$(uname -srm)\n$(cat /etc/os-release)\n"):
  Linux 5.13.0-28-generic x86_64
  NAME="Ubuntu"
  VERSION="20.04.2 LTS (Focal Fossa)"
  ID=ubuntu
  ID_LIKE=debian
  PRETTY_NAME="Ubuntu 20.04.2 LTS"
  VERSION_ID="20.04"
  HOME_URL="https://www.ubuntu.com/"
  SUPPORT_URL="https://help.ubuntu.com/"
  BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
  PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
  VERSION_CODENAME=focal
  UBUNTU_CODENAME=focal

• Version of Ansible (ansible --version):
  ansible 2.10.11

• Version of Python (python --version):
  Python 3.8.10

Kubespray version (commit) (git rev-parse --short HEAD):
master branch including 063fc52

Network plugin used:
calico

Command used to invoke ansible:
ansible-playbook -i inventory/cluster/inventory.ini --become --become-user=root cluster.yml

Anything else do we need to know:
with following (default) variables set:

enable_nodelocaldns: true
resolvconf_mode: host_resolvconf

the playbook creates /etc/systemd/resolved.conf with "DNS=169.254.25.10" although this ip is not yet reachable at the beginning. According to the document docs/dns-stack.md this problem is known and with using of dns_early and dns_late "fixed". But for systemd-resolved there is no difference configured in both stages.

Furthermore in docs/dns-stack.md it is written that upstream_dns_servers should be used in host_resolvconf mode. But configured upstream_dns_servers are not added to /etc/systemd/resolved.conf.

If both would work correct the same DNS problems occur on running reset.yml. After this playbook DNS resolution is broken because of "DNS=169.254.25.10".