systemd - use list-unit-files rather than list-units (#72363)

list-unit-files will return all files on the system. list-units omits those
that are disabled.

Co-authored-by: Ken Dreyer <ktdreyer@ktdreyer.com>

changelogs/fragments/71528-systemd-list-unit-files.yml

@@ -0,0 +1,5 @@
+bugfixes:
+  - >
+    systemd - follow up fix to https://github.com/ansible/ansible/issues/72338
+    to use ``list-unit-files`` rather than ``list-units`` in order to show
+    all units files on the system.

lib/ansible/modules/systemd.py

@@ -405,7 +405,7 @@ def main():
         elif err and rc == 1 and 'Failed to parse bus message' in err:
             result['status'] = parse_systemctl_show(to_native(out).split('\n'))
 
-            (rc, out, err) = module.run_command("{systemctl} list-units '{unit}*'".format(systemctl=systemctl, unit=unit))
+            (rc, out, err) = module.run_command("{systemctl} list-unit-files '{unit}*'".format(systemctl=systemctl, unit=unit))
             is_systemd = unit in out
 
             (rc, out, err) = module.run_command("{systemctl} is-active '{unit}'".format(systemctl=systemctl, unit=unit))