Add matrix_services_autostart_enabled variable for preventing services autostart

Some people requested that `--tags=start` not set up service autostart.

One can now do `--tags=start --extra-vars="matrix_services_autostart_enabled=false"`
to just start services ones and not set up autostarting.

roles/matrix-common-after/tasks/start.yml

@@ -1,5 +1,9 @@
 ---
 
+- name: Deterimne whether we should make services autostart
+  set_fact:
+    matrix_services_autostart_enabled_bool: "{{ true if matrix_services_autostart_enabled|default('') == '' else matrix_services_autostart_enabled|bool }}"
+
 - name: Ensure systemd is reloaded
   service:
     daemon_reload: yes
@@ -14,7 +18,7 @@
 - name: Ensure Matrix services are started
   service:
     name: "{{ item }}"
-    enabled: yes
+    enabled: "{{ matrix_services_autostart_enabled_bool }}"
     state: started
   with_items: "{{ matrix_systemd_services_list }}"
   when: not ansible_check_mode