Disable systemd services when stopping to uninstall them

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.

roles/matrix-coturn/tasks/setup_uninstall.yml

@@ -10,6 +10,7 @@
   service:
     name: matrix-coturn
     state: stopped
+    enabled: no
     daemon_reload: yes
   when: "matrix_coturn_service_stat.stat.exists|bool"
 
@@ -17,6 +18,7 @@
   service:
     name: matrix-coturn
     state: stopped
+    enabled: no
     daemon_reload: yes
   failed_when: false
   when: "matrix_coturn_service_stat.stat.exists|bool"