tools/systemd/time: convert the resulting timestamp into an option

we want to use dates for the calendarspec, and with that there are some
impossible combinations that cannot be detected during parsing
(e.g. some datetimes do not exist in some timezones, and the timezone
can change after setting the schedule)

so finding no timestamp is not an error anymore but a valid result

we omit logging in that case (since it is not an error anymore)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

src/api2/admin/sync.rs

@@ -57,7 +57,8 @@ pub fn list_sync_jobs(
         job.next_run = (|| -> Option<i64> {
             let schedule = job.schedule.as_ref()?;
             let event = parse_calendar_event(&schedule).ok()?;
-            compute_next_event(&event, last, false).ok()
+            // ignore errors
+            compute_next_event(&event, last, false).unwrap_or_else(|_| None)
         })();
     }