Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1749

Until now, we were leaving services "enabled"
(symlinks in /etc/systemd/system/multi-user.target.wants/).

We clean these up now. Broken symlinks may still exist in older
installations that enabled/disabled services. We're not taking care
to fix these up. It's just a cosmetic defect anyway.

Should have been done in 63f5a88fa0.

This reverts commit e913347fe1.

Without this the hydrogen task would fail for Ansible 2.7 even when hydrogen is not enabled.