Fix: Expired sessions were not closed.

cdstar-runtime/src/main/java/de/gwdg/cdstar/runtime/services/SessionRegistry.java

@@ -29,7 +29,9 @@ public class SessionRegistry implements SessionStartListener, SessionListener, R
 
 	@Override
 	public void onStartup(RuntimeContext ctx) throws Exception {
-		sessionReaper = ctx.lookupRequired(CronService.class).schedule(this::reapExpiredSessions, 10, TimeUnit.SECONDS);
+		sessionReaper = ctx.lookupRequired(CronService.class).scheduleWithFixedDelay(this::reapExpiredSessions, 60, 10,
+				TimeUnit.SECONDS);
+
 		ctx.lookup(MetricRegistry.class).ifPresent(mr -> {
 			mr.gauge("sess.open", () -> () -> allSessions.size());
 			mr.gauge("sess.open.ro", () -> () -> allSessions.values().stream()