Job "docker.service/start" failed with result 'dependency' when using an custom insecure registry

Issue

• When trying to start the docker.service in an OCP master node, it fails with the following error message:

  # systemctl start docker
  A dependency job for docker.service failed. See 'journalctl -xe' for details.
  

• The registries.service status has the following error message:

  # systemctl status registries
  [...]
  Feb 14 09:20:35 ocpmaster.example.com systemd[1]: Starting SystemWide Container Registries...
  Feb 14 09:20:35 ocpmaster.example.com registries[43156]: Unable to load and parse /etc/containers/registries.conf
  Feb 14 09:20:35 ocpmaster.example.com registries[43156]: .
  Feb 14 09:20:35 ocpmaster.example.com systemd[1]: registries.service: main process exited, code=exited, status=1/FAILURE
  Feb 14 09:20:35 ocpmaster.example.com systemd[1]: Failed to start SystemWide Container Registries.
  Feb 14 09:20:35 ocpmaster.example.com systemd[1]: Unit registries.service entered failed state.
  Feb 14 09:20:35 ocpmaster.example.com systemd[1]: registries.service failed.