Fixed missing logmessages

Files come and go quickly with a busy log stream:

[root@worker2 ~]# ls /var/log/pods/kolab_roundcube-b944bd67f-n4zrc_4709669e-def6-49d6-933e-87da28e9b849/roundcube/ -lh
total 27M
-rw-r----- 1 root root 4.4M Sep 2 09:47 0.log
-rw-r--r-- 1 root root 771K Sep 2 09:46 0.log.20250902-094641.gz
-rw-r--r-- 1 root root 781K Sep 2 09:47 0.log.20250902-094651.gz
-rw-r--r-- 1 root root 848K Sep 2 09:47 0.log.20250902-094701.gz
-rw-r----- 1 root root 12M Sep 2 09:47 0.log.20250902-094711

The more frequent scanning for files doesn't seem like a problem so far,
but I suppose 500ms is on the lower end of sensible values.